(svn r12042) -Fix [FS#1676]: Reimplement how rivers and canals are stored in the map, allowing the sea/river/canal status to also be

stored for buoys, docks, locks and depots. All these are now allowed on rivers and removal of them will revert to the 
original water type.

12 files changed, 161 insertions, 107 deletions

diff --git a/docs/landscape.html b/docs/landscape.html
index 99caa5d9f..5f21fc7c3 100644
--- a/docs/landscape.html
+++ b/docs/landscape.html
@@ -794,6 +794,7 @@
      <li>m3 bits 7..4: persistent random data for newstations</li>
      <li>m3 bits 3..0: <a href="#TrackType">track type</a> for railway stations</li>
      <li>m3 bits 2..0: present road types for road stops</li>
+     <li>m3 bits 1..0: water class for buoys and water part of docks</li>
      <li>m4: custom station id; 0 means standard graphics</li>
      <li>m5: graphics index (range from 0..255 for each station type):
       <table>
@@ -906,13 +907,14 @@
    <td>
     <ul>
      <li>m1: <a href="#OwnershipInfo">owner</a> (for sea, rivers, and coasts normally <tt>11</tt>)</li>
+     <li>m3 bits 1..0 : Water class (sea, canal or river)
      <li>m4: Owner of the water when ship depot</li>
      <li>m4: Random data for canal or river tiles</li>
      <li>m5: tile type:
       <table>
        <tr>
         <td nowrap valign=top><tt>00</tt>&nbsp; </td>
-        <td align=left>water</td>
+        <td align=left>water, canal or river</td>
        </tr>
 
        <tr>
@@ -921,11 +923,6 @@
        </tr>
 
        <tr>
-        <td noswap valign=top><tt>02</tt>&nbsp; </td>
-        <td align=left>river</td>
-       </tr>
-
-       <tr>
         <td nowrap valign=top><tt>10</tt>..<tt>1B</tt>&nbsp; </td>
         <td align=left>canal locks
          <table>
diff --git a/docs/landscape_grid.html b/docs/landscape_grid.html
index eb9ab8f82..b24d4a19a 100644
--- a/docs/landscape_grid.html
+++ b/docs/landscape_grid.html
@@ -216,7 +216,7 @@ the array so you can quickly see what is used and what is not.
       <td class="bits">-inherit-</td>
       <td class="bits">-inherit-</td>
       <td class="bits">-inherit-</td>
-      <td class="bits"><span class="free">OOOO OOOO</span></td>
+      <td class="bits"><span class="free">OOOO OO</span>XX</td>
       <td class="bits"><span class="option">~~~~ ~~~~</span></td>
       <td class="bits"><span class="option">~~~~ ~</span>XXX</td>
       <td class="bits"><span class="free">OO</span>XX X<span class="free">O</span>XX</td>
@@ -238,7 +238,7 @@ the array so you can quickly see what is used and what is not.
       <td class="bits">-inherit-</td>
       <td class="bits">-inherit-</td>
       <td class="bits">-inherit-</td>
-      <td class="bits"><span class="free">OOOO OOOO</span></td>
+      <td class="bits"><span class="free">OOOO OO</span>XX</td>
       <td class="bits"><span class="option">~~~~ ~~~~</span></td>
       <td class="bits"><span class="option">~~~~ ~~~~</span></td>
       <td class="bits"><span class="free">OO</span>XX X<span class="free">O</span>XX</td>
@@ -261,7 +261,7 @@ the array so you can quickly see what is used and what is not.
       <td class="bits">XXXX XXXX</td>
       <td class="bits"><span class="option">~~~</span>X XXXX</td>
       <td class="bits"><span class="free">OOOO OOOO OOOO OOOO</span></td>
-      <td class="bits"><span class="free">OOOO OOOO</span></td>
+      <td class="bits"><span class="free">OOOO OO</span>XX</td>
       <td class="bits"><span class="free">OOOO OOOO</span></td>
       <td class="bits">X<span class="option">~~</span>X XXXX</td>
       <td class="bits">XX<span class="free">OO OO</span>XX</td>
@@ -272,7 +272,7 @@ the array so you can quickly see what is used and what is not.
       <td class="bits">-inherit-</td>
       <td class="bits">-inherit-</td>
       <td class="bits"><span class="free">OOOO OOOO OOOO OOOO</span></td>
-      <td class="bits"><span class="free">OOOO OOOO</span></td>
+      <td class="bits"><span class="free">OOOO OO</span>XX</td>
       <td class="bits">XXXX XXXX</td>
       <td class="bits">-inherit-</td>
       <td class="bits">XX<span class="free">OO OO</span>XX</td>
@@ -283,7 +283,7 @@ the array so you can quickly see what is used and what is not.
       <td class="bits">-inherit-</td>
       <td class="bits">-inherit-</td>
       <td class="bits"><span class="free">OOOO OOOO OOOO OOOO</span></td>
-      <td class="bits"><span class="free">OOOO OOOO</span></td>
+      <td class="bits"><span class="free">OOOO OO</span>XX</td>
       <td class="bits">XXXX XXXX</td>
       <td class="bits">-inherit-</td>
       <td class="bits">XX<span class="free">OO OO</span>XX</td>
diff --git a/src/industry_cmd.cpp b/src/industry_cmd.cpp
index 2ef3cf353..d462b185b 100644
--- a/src/industry_cmd.cpp
+++ b/src/industry_cmd.cpp
@@ -1226,7 +1226,7 @@ static bool CheckIfIndustryTilesAreFree(TileIndex tile, const IndustryTileTable
 			IndustryBehaviour ind_behav = GetIndustrySpec(type)->behaviour;
 
 			/* Perform land/water check if not disabled */
-			if (!HasBit(its->slopes_refused, 5) && ((IsWaterTile(cur_tile) || IsRiverTile(cur_tile)) == !(ind_behav & INDUSTRYBEH_BUILT_ONWATER))) return false;
+			if (!HasBit(its->slopes_refused, 5) && (IsWaterTile(cur_tile) == !(ind_behav & INDUSTRYBEH_BUILT_ONWATER))) return false;
 
 			if (HasBit(its->callback_flags, CBM_INDT_SHAPE_CHECK)) {
 				custom_shape = true;
diff --git a/src/newgrf_canal.cpp b/src/newgrf_canal.cpp
index 1a276ea7d..df3d7630c 100644
--- a/src/newgrf_canal.cpp
+++ b/src/newgrf_canal.cpp
@@ -22,7 +22,8 @@ WaterFeature _water_feature[CF_END];
  * three functions are stubs. */
 static uint32 CanalGetRandomBits(const ResolverObject *object)
 {
-	return GetWaterTileRandomBits(object->u.canal.tile);
+	/* Return random bits only for water tiles, not station tiles */
+	return IsTileType(object->u.canal.tile, MP_WATER) ? GetWaterTileRandomBits(object->u.canal.tile) : 0;
 }
 
 
diff --git a/src/openttd.cpp b/src/openttd.cpp
index 736acb978..1b298de8b 100644
--- a/src/openttd.cpp
+++ b/src/openttd.cpp
@@ -77,6 +77,7 @@
 #include "tree_map.h"
 #include "tunnelbridge_map.h"
 #include "void_map.h"
+#include "water.h"
 
 #include <stdarg.h>
 
@@ -2323,9 +2324,31 @@ bool AfterLoadGame()
 	}
 
 	if (CheckSavegameVersion(86)) {
-		/* Now all crossings should be in correct state */
 		for (TileIndex t = 0; t < map_size; t++) {
+			/* Now all crossings should be in correct state */
 			if (IsLevelCrossingTile(t)) UpdateLevelCrossing(t, false);
+
+			/* Move river flag and update canals to use water class */
+			if (IsTileType(t, MP_WATER)) {
+				if (_m[t].m5 == 2) {
+					MakeRiver(t, Random());
+				} else {
+					Owner o = GetTileOwner(t);
+					if (IsWater(t) && o != OWNER_WATER) {
+						MakeCanal(t, o, Random());
+					}
+				}
+			}
+		}
+
+		/* Update locks, depots, docks and buoys to have a water class based
+		 * on its neighbouring tiles. Done after river and canal updates to
+		 * ensure neighbours are correct. */
+		for (TileIndex t = 0; t < map_size; t++) {
+			if (GetTileSlope(t, NULL) != SLOPE_FLAT) continue;
+
+			if (IsTileType(t, MP_WATER) && (GetWaterTileType(t) == WATER_TILE_LOCK || IsShipDepot(t))) SetWaterClassDependingOnSurroundings(t);
+			if (IsTileType(t, MP_STATION) && (IsDock(t) || IsBuoy(t))) SetWaterClassDependingOnSurroundings(t);
 		}
 	}
 
diff --git a/src/saveload.cpp b/src/saveload.cpp
index 008821df6..3b62a3991 100644
--- a/src/saveload.cpp
+++ b/src/saveload.cpp
@@ -34,7 +34,7 @@
 
 #include "table/strings.h"
 
-extern const uint16 SAVEGAME_VERSION = 85;
+extern const uint16 SAVEGAME_VERSION = 86;
 uint16 _sl_version;       ///< the major savegame version identifier
 byte   _sl_minor_version; ///< the minor savegame version, DO NOT USE!
 
diff --git a/src/station_cmd.cpp b/src/station_cmd.cpp
index b5749c4b8..538c68b72 100644
--- a/src/station_cmd.cpp
+++ b/src/station_cmd.cpp
@@ -1837,6 +1837,8 @@ CommandCost CmdBuildBuoy(TileIndex tile, uint32 flags, uint32 p1, uint32 p2)
 	if (!IsWaterTile(tile) || tile == 0) return_cmd_error(STR_304B_SITE_UNSUITABLE);
 	if (MayHaveBridgeAbove(tile) && IsBridgeAbove(tile)) return_cmd_error(STR_5007_MUST_DEMOLISH_BRIDGE_FIRST);
 
+	if (GetTileSlope(tile, NULL) != SLOPE_FLAT) return_cmd_error(STR_304B_SITE_UNSUITABLE);
+
 	/* allocate and initialize new station */
 	Station *st = new Station(tile);
 	if (st == NULL) return_cmd_error(STR_3008_TOO_MANY_STATIONS_LOADING);
@@ -1859,7 +1861,7 @@ CommandCost CmdBuildBuoy(TileIndex tile, uint32 flags, uint32 p1, uint32 p2)
 
 		st->build_date = _date;
 
-		MakeBuoy(tile, st->index);
+		MakeBuoy(tile, st->index, GetWaterClass(tile));
 
 		UpdateStationVirtCoordDirty(st);
 		UpdateStationAcceptance(st, false);
@@ -1917,7 +1919,7 @@ static CommandCost RemoveBuoy(Station *st, uint32 flags)
 		/* We have to set the water tile's state to the same state as before the
 		 * buoy was placed. Otherwise one could plant a buoy on a canal edge,
 		 * remove it and flood the land (if the canal edge is at level 0) */
-		MakeWaterOrCanalDependingOnOwner(tile, GetTileOwner(tile));
+		MakeWaterKeepingClass(tile, GetTileOwner(tile));
 		MarkTileDirtyByTile(tile);
 
 		UpdateStationVirtCoordDirty(st);
@@ -1951,7 +1953,7 @@ CommandCost CmdBuildDock(TileIndex tile, uint32 flags, uint32 p1, uint32 p2)
 	direction = ReverseDiagDir(direction);
 
 	/* Docks cannot be placed on rapids */
-	if (IsRiverTile(tile)) return_cmd_error(STR_304B_SITE_UNSUITABLE);
+	if (IsWaterTile(tile)) return_cmd_error(STR_304B_SITE_UNSUITABLE);
 
 	if (!(flags & DC_NO_TOWN_RATING) && !CheckIfAuthorityAllows(tile)) return CMD_ERROR;
 
@@ -1968,6 +1970,9 @@ CommandCost CmdBuildDock(TileIndex tile, uint32 flags, uint32 p1, uint32 p2)
 
 	if (MayHaveBridgeAbove(tile_cur) && IsBridgeAbove(tile_cur)) return_cmd_error(STR_5007_MUST_DEMOLISH_BRIDGE_FIRST);
 
+	/* Get the water class of the water tile before it is cleared.*/
+	WaterClass wc = GetWaterClass(tile_cur);
+
 	cost = DoCommand(tile_cur, 0, 0, flags, CMD_LANDSCAPE_CLEAR);
 	if (CmdFailed(cost)) return CMD_ERROR;
 
@@ -2025,7 +2030,7 @@ CommandCost CmdBuildDock(TileIndex tile, uint32 flags, uint32 p1, uint32 p2)
 
 		st->rect.BeforeAddRect(tile, _dock_w_chk[direction], _dock_h_chk[direction], StationRect::ADD_TRY);
 
-		MakeDock(tile, st->owner, st->index, direction);
+		MakeDock(tile, st->owner, st->index, direction, wc);
 
 		UpdateStationVirtCoordDirty(st);
 		UpdateStationAcceptance(st, false);
@@ -2050,7 +2055,7 @@ static CommandCost RemoveDock(Station *st, uint32 flags)
 
 	if (flags & DC_EXEC) {
 		DoClearSquare(tile1);
-		MakeWaterOrCanalDependingOnSurroundings(tile2, st->owner);
+		MakeWaterKeepingClass(tile2, st->owner);
 
 		st->rect.AfterRemoveTile(st, tile1);
 		st->rect.AfterRemoveTile(st, tile2);
@@ -2155,7 +2160,14 @@ static void DrawTile_Station(TileInfo *ti)
 		DrawTramCatenary(ti, axis == AXIS_X ? ROAD_X : ROAD_Y);
 	}
 
-	if (IsCanalBuoyTile(ti->tile)) DrawCanalWater(ti->tile);
+	if (IsBuoy(ti->tile)) {
+		/* Draw appropriate water edges */
+		switch (GetWaterClass(ti->tile)) {
+			case WATER_CLASS_SEA: break;
+			case WATER_CLASS_CANAL: DrawCanalWater(ti->tile, false); break;
+			case WATER_CLASS_RIVER: DrawRiverWater(ti, false); break;
+		}
+	}
 
 	const DrawTileSeqStruct *dtss;
 	foreach_draw_tile_seq(dtss, t->seq) {
diff --git a/src/station_map.h b/src/station_map.h
index b4e40ccef..f2a2f86dd 100644
--- a/src/station_map.h
+++ b/src/station_map.h
@@ -7,6 +7,7 @@
 
 #include "rail_map.h"
 #include "road_map.h"
+#include "water_map.h"
 #include "station.h"
 #include "rail.h"
 
@@ -155,16 +156,6 @@ static inline bool IsBuoyTile(TileIndex t)
 	return IsTileType(t, MP_STATION) && IsBuoy(t);
 }
 
-static inline bool IsCanalBuoyTile(TileIndex t)
-{
-	return IsBuoyTile(t) && !IsTileOwner(t, OWNER_WATER);
-}
-
-static inline bool IsSeaBuoyTile(TileIndex t)
-{
-	return IsBuoyTile(t) && IsTileOwner(t, OWNER_WATER);
-}
-
 static inline bool IsHangarTile(TileIndex t)
 {
 	return IsTileType(t, MP_STATION) && IsHangar(t);
@@ -287,18 +278,20 @@ static inline void MakeAirport(TileIndex t, Owner o, StationID sid, byte section
 	MakeStation(t, o, sid, STATION_AIRPORT, section);
 }
 
-static inline void MakeBuoy(TileIndex t, StationID sid)
+static inline void MakeBuoy(TileIndex t, StationID sid, WaterClass wc)
 {
 	/* Make the owner of the buoy tile the same as the current owner of the
 	 * water tile. In this way, we can reset the owner of the water to its
 	 * original state when the buoy gets removed. */
 	MakeStation(t, GetTileOwner(t), sid, STATION_BUOY, 0);
+	SetWaterClass(t, wc);
 }
 
-static inline void MakeDock(TileIndex t, Owner o, StationID sid, DiagDirection d)
+static inline void MakeDock(TileIndex t, Owner o, StationID sid, DiagDirection d, WaterClass wc)
 {
 	MakeStation(t, o, sid, STATION_DOCK, d);
 	MakeStation(t + TileOffsByDiagDir(d), o, sid, STATION_DOCK, GFX_DOCK_BASE_WATER_PART + DiagDirToAxis(d));
+	SetWaterClass(t + TileOffsByDiagDir(d), wc);
 }
 
 static inline void MakeOilrig(TileIndex t, StationID sid)
diff --git a/src/tunnelbridge_cmd.cpp b/src/tunnelbridge_cmd.cpp
index bb1a0e85c..c380d9452 100644
--- a/src/tunnelbridge_cmd.cpp
+++ b/src/tunnelbridge_cmd.cpp
@@ -248,7 +248,7 @@ CommandCost CmdBuildBridge(TileIndex end_tile, uint32 flags, uint32 p1, uint32 p
 	/* retrieve landscape height and ensure it's on land */
 	tile_start = TileXY(x, y);
 	tile_end = TileXY(sx, sy);
-	if (IsWaterTile(tile_start) || IsRiverTile(tile_start) || IsWaterTile(tile_end) || IsRiverTile(tile_end)) {
+	if (IsWaterTile(tile_start) || IsWaterTile(tile_end)) {
 		return_cmd_error(STR_02A0_ENDS_OF_BRIDGE_MUST_BOTH);
 	}
 
@@ -373,7 +373,7 @@ CommandCost CmdBuildBridge(TileIndex end_tile, uint32 flags, uint32 p1, uint32 p
 		switch (GetTileType(tile)) {
 			case MP_WATER:
 				if (!EnsureNoVehicleOnGround(tile)) return_cmd_error(STR_980E_SHIP_IN_THE_WAY);
-				if (!IsWater(tile) && !IsCoast(tile) && !IsRiver(tile)) goto not_valid_below;
+				if (!IsWater(tile) && !IsCoast(tile)) goto not_valid_below;
 				break;
 
 			case MP_RAILWAY:
@@ -468,7 +468,7 @@ CommandCost CmdBuildTunnel(TileIndex start_tile, uint32 flags, uint32 p1, uint32
 	direction = GetInclinedSlopeDirection(start_tileh);
 	if (direction == INVALID_DIAGDIR) return_cmd_error(STR_500B_SITE_UNSUITABLE_FOR_TUNNEL);
 
-	if (IsRiverTile(start_tile)) return_cmd_error(STR_3807_CAN_T_BUILD_ON_WATER);
+	if (IsWaterTile(start_tile)) return_cmd_error(STR_3807_CAN_T_BUILD_ON_WATER);
 
 	ret = DoCommand(start_tile, 0, 0, flags, CMD_LANDSCAPE_CLEAR);
 	if (CmdFailed(ret)) return ret;
@@ -522,7 +522,7 @@ CommandCost CmdBuildTunnel(TileIndex start_tile, uint32 flags, uint32 p1, uint32
 	/* if the command fails from here on we want the end tile to be highlighted */
 	_build_tunnel_endtile = end_tile;
 
-	if (IsRiverTile(end_tile)) return_cmd_error(STR_3807_CAN_T_BUILD_ON_WATER);
+	if (IsWaterTile(end_tile)) return_cmd_error(STR_3807_CAN_T_BUILD_ON_WATER);
 
 	/* slope of end tile must be complementary to the slope of the start tile */
 	if (end_tileh != ComplementSlope(start_tileh)) {
diff --git a/src/water.h b/src/water.h
index 94570612c..3eecc15f4 100644
--- a/src/water.h
+++ b/src/water.h
@@ -11,10 +11,11 @@ bool FloodHalftile(TileIndex t);
 void ConvertGroundTilesIntoWaterTiles();
 
 void DrawShipDepotSprite(int x, int y, int image);
-void DrawCanalWater(TileIndex tile);
+void DrawCanalWater(TileIndex tile, bool draw_base);
+void DrawRiverWater(const struct TileInfo *ti, bool draw_base);
 void DrawShoreTile(Slope tileh);
 
-void MakeWaterOrCanalDependingOnOwner(TileIndex tile, Owner o);
-void MakeWaterOrCanalDependingOnSurroundings(TileIndex t, Owner o);
+void MakeWaterKeepingClass(TileIndex tile, Owner o);
+void SetWaterClassDependingOnSurroundings(TileIndex t);
 
 #endif /* WATER_H */
diff --git a/src/water_cmd.cpp b/src/water_cmd.cpp
index 55e297f38..5f73b526c 100644
--- a/src/water_cmd.cpp
+++ b/src/water_cmd.cpp
@@ -101,21 +101,16 @@ static void MarkCanalsAndRiversAroundDirty(TileIndex tile)
  * @param t the tile to change.
  * @param o the owner of the new tile.
  */
-void MakeWaterOrCanalDependingOnSurroundings(TileIndex t, Owner o)
+void SetWaterClassDependingOnSurroundings(TileIndex t)
 {
 	assert(GetTileSlope(t, NULL) == SLOPE_FLAT);
 
 	/* Mark tile dirty in all cases */
 	MarkTileDirtyByTile(t);
 
-	/* Non-sealevel -> canal */
-	if (TileHeight(t) != 0) {
-		MakeCanal(t, o, Random());
-		return;
-	}
-
 	bool has_water = false;
 	bool has_canal = false;
+	bool has_river = false;
 
 	for (DiagDirection dir = DIAGDIR_BEGIN; dir < DIAGDIR_END; dir++) {
 		TileIndex neighbour = TileAddByDiagDir(t, dir);
@@ -123,6 +118,7 @@ void MakeWaterOrCanalDependingOnSurroundings(TileIndex t, Owner o)
 			case MP_WATER:
 				has_water |= IsSea(neighbour) || IsCoast(neighbour) || (IsShipDepot(neighbour) && GetShipDepotWaterOwner(neighbour) == OWNER_WATER);
 				has_canal |= IsCanal(neighbour) || (IsShipDepot(neighbour) && GetShipDepotWaterOwner(neighbour) != OWNER_WATER);
+				has_river |= IsRiver(neighbour);
 				break;
 
 			case MP_RAILWAY:
@@ -138,10 +134,13 @@ void MakeWaterOrCanalDependingOnSurroundings(TileIndex t, Owner o)
 			default: break;
 		}
 	}
-	if (has_canal || !has_water) {
-		MakeCanal(t, o, Random());
+
+	if (has_river && !has_canal) {
+		SetWaterClass(t, WATER_CLASS_RIVER);
+	} else if (has_canal || !has_water) {
+		SetWaterClass(t, WATER_CLASS_CANAL);
 	} else {
-		MakeWater(t);
+		SetWaterClass(t, WATER_CLASS_SEA);
 	}
 }
 
@@ -162,11 +161,19 @@ CommandCost CmdBuildShipDepot(TileIndex tile, uint32 flags, uint32 p1, uint32 p2
 
 	tile2 = tile + (axis == AXIS_X ? TileDiffXY(1, 0) : TileDiffXY(0, 1));
 
-	if (!IsWaterTile(tile) || !IsWaterTile(tile2))
+	if (!IsWaterTile(tile) || !IsWaterTile(tile2)) {
 		return_cmd_error(STR_3801_MUST_BE_BUILT_ON_WATER);
+	}
 
 	if (IsBridgeAbove(tile) || IsBridgeAbove(tile2)) return_cmd_error(STR_5007_MUST_DEMOLISH_BRIDGE_FIRST);
 
+	if (GetTileSlope(tile, NULL) != SLOPE_FLAT || GetTileSlope(tile2, NULL) != SLOPE_FLAT) {
+		/* Prevent depots on rapids */
+		return_cmd_error(STR_0239_SITE_UNSUITABLE);
+	}
+
+	WaterClass wc1 = GetWaterClass(tile);
+	WaterClass wc2 = GetWaterClass(tile2);
 	Owner o1 = GetTileOwner(tile);
 	Owner o2 = GetTileOwner(tile2);
 	ret = DoCommand(tile, 0, 0, flags, CMD_LANDSCAPE_CLEAR);
@@ -181,8 +188,8 @@ CommandCost CmdBuildShipDepot(TileIndex tile, uint32 flags, uint32 p1, uint32 p2
 	if (flags & DC_EXEC) {
 		depot->town_index = ClosestTownFromTile(tile, (uint)-1)->index;
 
-		MakeShipDepot(tile,  _current_player, DEPOT_NORTH, axis, o1);
-		MakeShipDepot(tile2, _current_player, DEPOT_SOUTH, axis, o2);
+		MakeShipDepot(tile,  _current_player, DEPOT_NORTH, axis, wc1, o1);
+		MakeShipDepot(tile2, _current_player, DEPOT_SOUTH, axis, wc2, o2);
 		MarkTileDirtyByTile(tile);
 		MarkTileDirtyByTile(tile2);
 		d_auto_delete.Detach();
@@ -191,12 +198,14 @@ CommandCost CmdBuildShipDepot(TileIndex tile, uint32 flags, uint32 p1, uint32 p2
 	return CommandCost(EXPENSES_CONSTRUCTION, _price.build_ship_depot);
 }
 
-void MakeWaterOrCanalDependingOnOwner(TileIndex tile, Owner o)
+void MakeWaterKeepingClass(TileIndex tile, Owner o)
 {
-	if (o == OWNER_WATER) {
-		MakeWater(tile);
-	} else {
-		MakeCanal(tile, o, Random());
+	assert(IsTileType(tile, MP_WATER) || (IsTileType(tile, MP_STATION) && (IsBuoy(tile) || IsDock(tile))));
+
+	switch (GetWaterClass(tile)) {
+		case WATER_CLASS_SEA:   MakeWater(tile);              break;
+		case WATER_CLASS_CANAL: MakeCanal(tile, o, Random()); break;
+		case WATER_CLASS_RIVER: MakeRiver(tile, Random());    break;
 	}
 }
 
@@ -216,8 +225,8 @@ static CommandCost RemoveShipDepot(TileIndex tile, uint32 flags)
 		/* Kill the depot, which is registered at the northernmost tile. Use that one */
 		delete GetDepotByTile(tile2 < tile ? tile2 : tile);
 
-		MakeWaterOrCanalDependingOnOwner(tile,  GetShipDepotWaterOwner(tile));
-		MakeWaterOrCanalDependingOnOwner(tile2, GetShipDepotWaterOwner(tile2));
+		MakeWaterKeepingClass(tile,  GetShipDepotWaterOwner(tile));
+		MakeWaterKeepingClass(tile2, GetShipDepotWaterOwner(tile2));
 		MarkTileDirtyByTile(tile);
 		MarkTileDirtyByTile(tile2);
 	}
@@ -237,6 +246,8 @@ static CommandCost DoBuildShiplift(TileIndex tile, DiagDirection dir, uint32 fla
 
 	delta = TileOffsByDiagDir(dir);
 	/* lower tile */
+	WaterClass wc_lower = IsWaterTile(tile - delta) ? GetWaterClass(tile - delta) : WATER_CLASS_CANAL;
+
 	ret = DoCommand(tile - delta, 0, 0, flags, CMD_LANDSCAPE_CLEAR);
 	if (CmdFailed(ret)) return CMD_ERROR;
 	if (GetTileSlope(tile - delta, NULL) != SLOPE_FLAT) {
@@ -244,6 +255,8 @@ static CommandCost DoBuildShiplift(TileIndex tile, DiagDirection dir, uint32 fla
 	}
 
 	/* upper tile */
+	WaterClass wc_upper = IsWaterTile(tile + delta) ? GetWaterClass(tile + delta) : WATER_CLASS_CANAL;
+
 	ret = DoCommand(tile + delta, 0, 0, flags, CMD_LANDSCAPE_CLEAR);
 	if (CmdFailed(ret)) return CMD_ERROR;
 	if (GetTileSlope(tile + delta, NULL) != SLOPE_FLAT) {
@@ -257,7 +270,7 @@ static CommandCost DoBuildShiplift(TileIndex tile, DiagDirection dir, uint32 fla
 	}
 
 	if (flags & DC_EXEC) {
-		MakeLock(tile, _current_player, dir);
+		MakeLock(tile, _current_player, dir, wc_lower, wc_upper);
 		MarkTileDirtyByTile(tile);
 		MarkTileDirtyByTile(tile - delta);
 		MarkTileDirtyByTile(tile + delta);
@@ -280,8 +293,10 @@ static CommandCost RemoveShiplift(TileIndex tile, uint32 flags)
 
 	if (flags & DC_EXEC) {
 		DoClearSquare(tile);
-		MakeWaterOrCanalDependingOnSurroundings(tile + delta, _current_player);
-		MakeWaterOrCanalDependingOnSurroundings(tile - delta, _current_player);
+		MakeWaterKeepingClass(tile + delta, GetTileOwner(tile));
+		MakeWaterKeepingClass(tile - delta, GetTileOwner(tile));
+		MarkTileDirtyByTile(tile - delta);
+		MarkTileDirtyByTile(tile + delta);
 		MarkCanalsAndRiversAroundDirty(tile - delta);
 		MarkCanalsAndRiversAroundDirty(tile + delta);
 	}
@@ -301,7 +316,7 @@ CommandCost CmdBuildLock(TileIndex tile, uint32 flags, uint32 p1, uint32 p2)
 	if (dir == INVALID_DIAGDIR) return_cmd_error(STR_1000_LAND_SLOPED_IN_WRONG_DIRECTION);
 
 	/* Disallow building of locks on river rapids */
-	if (IsRiverTile(tile)) return_cmd_error(STR_0239_SITE_UNSUITABLE);
+	if (IsWaterTile(tile)) return_cmd_error(STR_0239_SITE_UNSUITABLE);
 
 	return DoBuildShiplift(tile, dir, flags);
 }
@@ -379,7 +394,6 @@ static CommandCost ClearTile_Water(TileIndex tile, byte flags)
 {
 	switch (GetWaterTileType(tile)) {
 		case WATER_TILE_CLEAR:
-		case WATER_TILE_RIVER:
 			if (flags & DC_NO_WATER) return_cmd_error(STR_3807_CAN_T_BUILD_ON_WATER);
 
 			/* Make sure it's not an edge tile. */
@@ -472,7 +486,7 @@ static bool IsWateredTile(TileIndex tile, Direction from)
 			}
 			return false;
 
-		case MP_STATION:  return IsOilRig(tile) || IsDock(tile) || IsBuoy(tile);
+		case MP_STATION:  return IsOilRig(tile) || (IsDock(tile) && GetTileSlope(tile, NULL) == SLOPE_FLAT) || IsBuoy(tile);
 		case MP_INDUSTRY: return (GetIndustrySpec(GetIndustryType(tile))->behaviour & INDUSTRYBEH_BUILT_ONWATER) != 0;
 		default:          return false;
 	}
@@ -518,9 +532,17 @@ static void DrawWaterEdges(SpriteID base, TileIndex tile)
 	}
 }
 
+/** Draw a plain sea water tile with no edges */
+void DrawSeaWater(TileIndex tile)
+{
+	DrawGroundSprite(SPR_FLAT_WATER_TILE, PAL_NONE);
+}
+
 /** draw a canal styled water tile with dikes around */
-void DrawCanalWater(TileIndex tile)
+void DrawCanalWater(TileIndex tile, bool draw_base)
 {
+	if (draw_base) DrawGroundSprite(SPR_FLAT_WATER_TILE, PAL_NONE);
+
 	/* Test for custom graphics, else use the default */
 	SpriteID dikes_base = GetCanalSprite(CF_DIKES, tile);
 	if (dikes_base == 0) dikes_base = SPR_CANAL_DIKES_BASE;
@@ -566,7 +588,7 @@ static void DrawWaterStuff(const TileInfo *ti, const WaterDrawTileStruct *wdts,
 	}
 }
 
-static void DrawRiverWater(const TileInfo *ti)
+void DrawRiverWater(const TileInfo *ti, bool draw_base)
 {
 	SpriteID image = SPR_FLAT_WATER_TILE;
 	SpriteID edges_base = GetCanalSprite(CF_RIVER_EDGE, ti->tile);
@@ -592,7 +614,7 @@ static void DrawRiverWater(const TileInfo *ti)
 		}
 	}
 
-	DrawGroundSprite(image, PAL_NONE);
+	if (draw_base) DrawGroundSprite(image, PAL_NONE);
 
 	/* Draw river edges if available. */
 	if (edges_base > 48) DrawWaterEdges(edges_base, ti->tile);
@@ -619,8 +641,11 @@ static void DrawTile_Water(TileInfo *ti)
 {
 	switch (GetWaterTileType(ti->tile)) {
 		case WATER_TILE_CLEAR:
-			DrawGroundSprite(SPR_FLAT_WATER_TILE, PAL_NONE);
-			if (IsCanal(ti->tile)) DrawCanalWater(ti->tile);
+			switch (GetWaterClass(ti->tile)) {
+				case WATER_CLASS_SEA:   DrawSeaWater(ti->tile); break;
+				case WATER_CLASS_CANAL: DrawCanalWater(ti->tile, true); break;
+				case WATER_CLASS_RIVER: DrawRiverWater(ti, true); break;
+			}
 			DrawBridgeMiddle(ti);
 			break;
 
@@ -637,11 +662,6 @@ static void DrawTile_Water(TileInfo *ti)
 		case WATER_TILE_DEPOT:
 			DrawWaterStuff(ti, _shipdepot_display_seq[GetSection(ti->tile)], PLAYER_SPRITE_COLOR(GetTileOwner(ti->tile)), 0);
 			break;
-
-		case WATER_TILE_RIVER:
-			DrawRiverWater(ti);
-			DrawBridgeMiddle(ti);
-			break;
 	}
 }
 
@@ -680,7 +700,6 @@ static void GetTileDesc_Water(TileIndex tile, TileDesc *td)
 {
 	switch (GetWaterTileType(tile)) {
 		case WATER_TILE_CLEAR:
-		case WATER_TILE_RIVER:
 			if (!IsCanal(tile)) {
 				td->str = STR_3804_WATER;
 			} else {
@@ -842,7 +861,7 @@ static FloodingBehaviour GetFloodingBehaviour(TileIndex tile)
 				Slope tileh = GetTileSlope(tile, NULL);
 				return (IsSlopeWithOneCornerRaised(tileh) ? FLOOD_ACTIVE : FLOOD_DRYUP);
 			} else {
-				return ((IsSea(tile) || (IsShipDepot(tile) && (GetShipDepotWaterOwner(tile) == OWNER_WATER))) ? FLOOD_ACTIVE : FLOOD_NONE);
+				return (GetWaterClass(tile) == WATER_CLASS_SEA) ? FLOOD_ACTIVE : FLOOD_NONE;
 			}
 
 		case MP_RAILWAY:
@@ -855,7 +874,7 @@ static FloodingBehaviour GetFloodingBehaviour(TileIndex tile)
 			return (GetTreeGround(tile) == TREE_GROUND_SHORE ? FLOOD_DRYUP : FLOOD_NONE);
 
 		case MP_STATION:
-			if (IsSeaBuoyTile(tile)) return FLOOD_ACTIVE;
+			if (IsBuoy(tile) && GetWaterClass(tile) == WATER_CLASS_SEA) return FLOOD_ACTIVE;
 			if (IsOilRig(tile) || IsDock(tile)) return FLOOD_PASSIVE;
 			return FLOOD_NONE;
 
@@ -1073,11 +1092,10 @@ static uint32 GetTileTrackStatus_Water(TileIndex tile, TransportType mode, uint
 	if (mode != TRANSPORT_WATER) return 0;
 
 	switch (GetWaterTileType(tile)) {
-		case WATER_TILE_CLEAR: ts = TRACK_BIT_ALL; break;
+		case WATER_TILE_CLEAR: ts = (GetTileSlope(tile, NULL) == SLOPE_FLAT) ? TRACK_BIT_ALL : TRACK_BIT_NONE; break;
 		case WATER_TILE_COAST: ts = (TrackBits)coast_tracks[GetTileSlope(tile, NULL) & 0xF]; break;
 		case WATER_TILE_LOCK:  ts = AxisToTrackBits(DiagDirToAxis(GetLockDirection(tile))); break;
 		case WATER_TILE_DEPOT: ts = AxisToTrackBits(GetShipDepotAxis(tile)); break;
-		case WATER_TILE_RIVER: ts = (GetTileSlope(tile, NULL) == SLOPE_FLAT) ? TRACK_BIT_ALL : TRACK_BIT_NONE; break;
 		default: return 0;
 	}
 	if (TileX(tile) == 0) {
diff --git a/src/water_map.h b/src/water_map.h
index d7d0b0ba8..b9bb4344a 100644
--- a/src/water_map.h
+++ b/src/water_map.h
@@ -10,7 +10,12 @@ enum WaterTileType {
 	WATER_TILE_COAST,
 	WATER_TILE_LOCK,
 	WATER_TILE_DEPOT,
-	WATER_TILE_RIVER,
+};
+
+enum WaterClass {
+	WATER_CLASS_SEA,
+	WATER_CLASS_CANAL,
+	WATER_CLASS_RIVER,
 };
 
 enum DepotPart {
@@ -32,13 +37,24 @@ static inline WaterTileType GetWaterTileType(TileIndex t)
 
 	if (_m[t].m5 == 0) return WATER_TILE_CLEAR;
 	if (_m[t].m5 == 1) return WATER_TILE_COAST;
-	if (_m[t].m5 == 2) return WATER_TILE_RIVER;
 	if (IsInsideMM(_m[t].m5, LOCK_MIDDLE, LOCK_END)) return WATER_TILE_LOCK;
 
 	assert(IsInsideMM(_m[t].m5, DEPOT_NORTH, DEPOT_END));
 	return WATER_TILE_DEPOT;
 }
 
+static inline WaterClass GetWaterClass(TileIndex t)
+{
+	assert(IsTileType(t, MP_WATER) || IsTileType(t, MP_STATION));
+	return (WaterClass)GB(_m[t].m3, 0, 2);
+}
+
+static inline void SetWaterClass(TileIndex t, WaterClass wc)
+{
+	assert(IsTileType(t, MP_WATER) || IsTileType(t, MP_STATION));
+	SB(_m[t].m3, 0, 2, wc);
+}
+
 /** IsWater return true if any type of clear water like ocean, river, canal */
 static inline bool IsWater(TileIndex t)
 {
@@ -47,24 +63,17 @@ static inline bool IsWater(TileIndex t)
 
 static inline bool IsSea(TileIndex t)
 {
-	if (GetWaterTileType(t) != WATER_TILE_CLEAR) return false;
-	if (!IsTileOwner(t, OWNER_WATER)) return false; // 'Human' built water = canal, not sea
-	return true;
-}
-
-static inline bool IsCoast(TileIndex t)
-{
-	return GetWaterTileType(t) == WATER_TILE_COAST;
+	return IsWater(t) && GetWaterClass(t) == WATER_CLASS_SEA;
 }
 
 static inline bool IsCanal(TileIndex t)
 {
-	return GetWaterTileType(t) == WATER_TILE_CLEAR && GetTileOwner(t) != OWNER_WATER;
+	return IsWater(t) && GetWaterClass(t) == WATER_CLASS_CANAL;
 }
 
 static inline bool IsRiver(TileIndex t)
 {
-	return GetWaterTileType(t) == WATER_TILE_RIVER;
+	return IsWater(t) && GetWaterClass(t) == WATER_CLASS_RIVER;
 }
 
 static inline bool IsWaterTile(TileIndex t)
@@ -72,9 +81,9 @@ static inline bool IsWaterTile(TileIndex t)
 	return IsTileType(t, MP_WATER) && IsWater(t);
 }
 
-static inline bool IsRiverTile(TileIndex t)
+static inline bool IsCoast(TileIndex t)
 {
-	return IsTileType(t, MP_WATER) && IsRiver(t);
+	return GetWaterTileType(t) == WATER_TILE_COAST;
 }
 
 static inline TileIndex GetOtherShipDepotTile(TileIndex t)
@@ -124,7 +133,7 @@ static inline void MakeWater(TileIndex t)
 	SetTileType(t, MP_WATER);
 	SetTileOwner(t, OWNER_WATER);
 	_m[t].m2 = 0;
-	_m[t].m3 = 0;
+	_m[t].m3 = WATER_CLASS_SEA;
 	_m[t].m4 = 0;
 	_m[t].m5 = 0;
 }
@@ -144,9 +153,9 @@ static inline void MakeRiver(TileIndex t, uint8 random_bits)
 	SetTileType(t, MP_WATER);
 	SetTileOwner(t, OWNER_WATER);
 	_m[t].m2 = 0;
-	_m[t].m3 = 0;
+	_m[t].m3 = WATER_CLASS_RIVER;
 	_m[t].m4 = random_bits;
-	_m[t].m5 = 2;
+	_m[t].m5 = 0;
 }
 
 static inline void MakeCanal(TileIndex t, Owner o, uint8 random_bits)
@@ -155,38 +164,38 @@ static inline void MakeCanal(TileIndex t, Owner o, uint8 random_bits)
 	SetTileType(t, MP_WATER);
 	SetTileOwner(t, o);
 	_m[t].m2 = 0;
-	_m[t].m3 = 0;
+	_m[t].m3 = WATER_CLASS_CANAL;
 	_m[t].m4 = random_bits;
 	_m[t].m5 = 0;
 }
 
-static inline void MakeShipDepot(TileIndex t, Owner o, DepotPart base, Axis a, Owner original_owner)
+static inline void MakeShipDepot(TileIndex t, Owner o, DepotPart base, Axis a, WaterClass original_water_class, Owner original_owner)
 {
 	SetTileType(t, MP_WATER);
 	SetTileOwner(t, o);
 	_m[t].m2 = 0;
-	_m[t].m3 = 0;
+	_m[t].m3 = original_water_class;
 	_m[t].m4 = original_owner;
 	_m[t].m5 = base + a * 2;
 }
 
-static inline void MakeLockTile(TileIndex t, Owner o, byte section)
+static inline void MakeLockTile(TileIndex t, Owner o, byte section, WaterClass original_water_class)
 {
 	SetTileType(t, MP_WATER);
 	SetTileOwner(t, o);
 	_m[t].m2 = 0;
-	_m[t].m3 = 0;
+	_m[t].m3 = original_water_class;
 	_m[t].m4 = 0;
 	_m[t].m5 = section;
 }
 
-static inline void MakeLock(TileIndex t, Owner o, DiagDirection d)
+static inline void MakeLock(TileIndex t, Owner o, DiagDirection d, WaterClass wc_lower, WaterClass wc_upper)
 {
 	TileIndexDiff delta = TileOffsByDiagDir(d);
 
-	MakeLockTile(t, o, LOCK_MIDDLE + d);
-	MakeLockTile(t - delta, o, LOCK_LOWER + d);
-	MakeLockTile(t + delta, o, LOCK_UPPER + d);
+	MakeLockTile(t, o, LOCK_MIDDLE + d, WATER_CLASS_CANAL);
+	MakeLockTile(t - delta, o, LOCK_LOWER + d, wc_lower);
+	MakeLockTile(t + delta, o, LOCK_UPPER + d, wc_upper);
 }
 
 #endif /* WATER_MAP_H */