Index: src/station_cmd.cpp
===================================================================
--- src/station_cmd.cpp	(revision 27632)
+++ src/station_cmd.cpp	(working copy)
@@ -2504,6 +2504,14 @@
 		return_cmd_error(STR_ERROR_SITE_UNSUITABLE);
 	}
 
+	if (HasTileWaterClass(tile_cur)) {
+		TrackBits tb = TrackStatusToTrackBits(GetTileTrackStatus(tile_cur, TRANSPORT_WATER, 0));
+		if (((direction == DIAGDIR_SW && (tb & TRACK_BIT_3WAY_NE) != 0) || (direction == DIAGDIR_NW && (tb & TRACK_BIT_3WAY_SE) != 0) || (direction == DIAGDIR_SE && (tb & TRACK_BIT_3WAY_NW) != 0) || (direction == DIAGDIR_NE && (tb & TRACK_BIT_3WAY_SW) != 0) && !IsShipDepotTile(tile_cur) && IsTileType(tile_cur, MP_WATER) && !IsLock(tile_cur))) {
+			ret = EnsureNoVehicleOnGround(tile_cur);
+			if (ret.Failed()) return ret;
+		}
+	}
+
 	TileArea dock_area = TileArea(tile + ToTileIndexDiff(_dock_tileoffs_chkaround[direction]),
 			_dock_w_chk[direction], _dock_h_chk[direction]);
 
Index: src/water_cmd.cpp
===================================================================
--- src/water_cmd.cpp	(revision 27632)
+++ src/water_cmd.cpp	(working copy)
@@ -135,6 +135,39 @@
 		cost.AddCost(ret);
 	}
 
+	TrackBits tb;
+	TileIndex tc = tile + (axis == AXIS_X ? TileDiffXY(0, -1) : TileDiffXY(1, 0));
+	if (HasTileWaterClass(tc)) {
+		tb = TrackStatusToTrackBits(GetTileTrackStatus(tc, TRANSPORT_WATER, 0));
+		if (((axis == AXIS_Y && (tb & TRACK_BIT_3WAY_NE) != 0) || (axis == AXIS_X && (tb & TRACK_BIT_3WAY_SE) != 0) && !IsShipDepotTile(tc) && IsTileType(tc, MP_WATER) && !IsLock(tc))) {
+			ret = EnsureNoVehicleOnGround(tc);
+			if (ret.Failed()) return ret;
+		}
+	}
+	tc = tile2 + (axis == AXIS_X ? TileDiffXY(0, -1) : TileDiffXY(1, 0));
+	if (HasTileWaterClass(tc)) {
+		tb = TrackStatusToTrackBits(GetTileTrackStatus(tc, TRANSPORT_WATER, 0));
+		if (((axis == AXIS_Y && (tb & TRACK_BIT_3WAY_NE) != 0) || (axis == AXIS_X && (tb & TRACK_BIT_3WAY_SE) != 0) && !IsShipDepotTile(tc) && IsTileType(tc, MP_WATER) && !IsLock(tc))) {
+			ret = EnsureNoVehicleOnGround(tc);
+			if (ret.Failed()) return ret;
+		}
+	}
+	tc = tile + (axis == AXIS_X ? TileDiffXY(0, 1) : TileDiffXY(-1, 0));
+	if (HasTileWaterClass(tc)) {
+		tb = TrackStatusToTrackBits(GetTileTrackStatus(tc, TRANSPORT_WATER, 0));
+		if (((axis == AXIS_Y && (tb & TRACK_BIT_3WAY_SW) != 0) || (axis == AXIS_X && (tb & TRACK_BIT_3WAY_NW) != 0) && !IsShipDepotTile(tc) && IsTileType(tc, MP_WATER) && !IsLock(tc))) {
+			ret = EnsureNoVehicleOnGround(tc);
+			if (ret.Failed()) return ret;
+		}
+	}
+	tc = tile2 + (axis == AXIS_X ? TileDiffXY(0, 1) : TileDiffXY(-1, 0));
+	if (HasTileWaterClass(tc)) {
+		tb = TrackStatusToTrackBits(GetTileTrackStatus(tc, TRANSPORT_WATER, 0));
+		if (((axis == AXIS_Y && (tb & TRACK_BIT_3WAY_SW) != 0) || (axis == AXIS_X && (tb & TRACK_BIT_3WAY_NW) != 0) && !IsShipDepotTile(tc) && IsTileType(tc, MP_WATER) && !IsLock(tc))) {
+			ret = EnsureNoVehicleOnGround(tc);
+			if (ret.Failed()) return ret;
+		}
+	}
 	if (flags & DC_EXEC) {
 		Depot *depot = new Depot(tile);
 		depot->build_date = _date;
@@ -372,6 +405,41 @@
 	DiagDirection dir = GetInclinedSlopeDirection(GetTileSlope(tile));
 	if (dir == INVALID_DIAGDIR) return_cmd_error(STR_ERROR_LAND_SLOPED_IN_WRONG_DIRECTION);
 
+	Axis axis = DiagDirToAxis(dir);
+	TrackBits tb;
+	CommandCost ret;
+	TileIndex tc = tile + (axis == AXIS_X ? TileDiffXY(-1, -1) : TileDiffXY(1, -1));
+	if (HasTileWaterClass(tc)) {
+		tb = TrackStatusToTrackBits(GetTileTrackStatus(tc, TRANSPORT_WATER, 0));
+		if (((axis == AXIS_Y && (tb & TRACK_BIT_3WAY_NE) != 0) || (axis == AXIS_X && (tb & TRACK_BIT_3WAY_SE) != 0) && !IsShipDepotTile(tc) && IsTileType(tc, MP_WATER) && !IsLock(tc))) {
+			ret = EnsureNoVehicleOnGround(tc);
+			if (ret.Failed()) return ret;
+		}
+	}
+	tc = tile + (axis == AXIS_X ? TileDiffXY(1, -1) : TileDiffXY(1, 1));
+	if (HasTileWaterClass(tc)) {
+		tb = TrackStatusToTrackBits(GetTileTrackStatus(tc, TRANSPORT_WATER, 0));
+		if (((axis == AXIS_Y && (tb & TRACK_BIT_3WAY_NE) != 0) || (axis == AXIS_X && (tb & TRACK_BIT_3WAY_SE) != 0) && !IsShipDepotTile(tc) && IsTileType(tc, MP_WATER) && !IsLock(tc))) {
+			ret = EnsureNoVehicleOnGround(tc);
+			if (ret.Failed()) return ret;
+		}
+	}
+	tc = tile + (axis == AXIS_X ? TileDiffXY(-1, 1) : TileDiffXY(-1, -1));
+	if (HasTileWaterClass(tc)) {
+		tb = TrackStatusToTrackBits(GetTileTrackStatus(tc, TRANSPORT_WATER, 0));
+		if (((axis == AXIS_Y && (tb & TRACK_BIT_3WAY_SW) != 0) || (axis == AXIS_X && (tb & TRACK_BIT_3WAY_NW) != 0) && !IsShipDepotTile(tc) && IsTileType(tc, MP_WATER) && !IsLock(tc))) {
+			ret = EnsureNoVehicleOnGround(tc);
+			if (ret.Failed()) return ret;
+		}
+	}
+	tc = tile + (axis == AXIS_X ? TileDiffXY(1, 1) : TileDiffXY(-1, 1));
+	if (HasTileWaterClass(tc)) {
+		tb = TrackStatusToTrackBits(GetTileTrackStatus(tc, TRANSPORT_WATER, 0));
+		if (((axis == AXIS_Y && (tb & TRACK_BIT_3WAY_SW) != 0) || (axis == AXIS_X && (tb & TRACK_BIT_3WAY_NW) != 0) && !IsShipDepotTile(tc) && IsTileType(tc, MP_WATER) && !IsLock(tc))) {
+			ret = EnsureNoVehicleOnGround(tc);
+			if (ret.Failed()) return ret;
+		}
+	}
 	return DoBuildLock(tile, dir, flags);
 }