Fix water infrastructure accounting when building ship depots

See: https://github.com/OpenTTD/OpenTTD/issues/10419

src/water_cmd.cpp

@@ -148,11 +148,12 @@ CommandCost CmdBuildShipDepot(TileIndex tile, DoCommandFlag flags, uint32 p1, ui
 		Depot *depot = new Depot(tile);
 		depot->build_date = _date;
 
-		if (wc1 == WATER_CLASS_CANAL || wc2 == WATER_CLASS_CANAL) {
-			/* Update infrastructure counts after the unconditional clear earlier. */
-			Company::Get(_current_company)->infrastructure.water += wc1 == WATER_CLASS_CANAL && wc2 == WATER_CLASS_CANAL ? 2 : 1;
-		}
-		Company::Get(_current_company)->infrastructure.water += 2 * LOCK_DEPOT_TILE_FACTOR;
+		uint new_water_infra = 2 * LOCK_DEPOT_TILE_FACTOR;
+		/* Update infrastructure counts after the tile clears earlier. */
+		if (wc1 == WATER_CLASS_CANAL && !(HasTileWaterClass(tile) && GetWaterClass(tile) == WATER_CLASS_CANAL && IsTileOwner(tile, _current_company))) new_water_infra++;
+		if (wc2 == WATER_CLASS_CANAL && !(HasTileWaterClass(tile2) && GetWaterClass(tile2) == WATER_CLASS_CANAL && IsTileOwner(tile2, _current_company))) new_water_infra++;
+
+		Company::Get(_current_company)->infrastructure.water += new_water_infra;
 		DirtyCompanyInfrastructureWindows(_current_company);
 
 		MakeShipDepot(tile,  _current_company, depot->index, DEPOT_PART_NORTH, axis, wc1);