diff --git a/water_cmd.c b/water_cmd.c
--- a/water_cmd.c
+++ b/water_cmd.c
@@ -148,7 +148,7 @@ static int32 DoBuildShiplift(TileIndex t
 	}
 
 	if (flags & DC_EXEC) {
-		MakeLock(tile, dir);
+		MakeLock(tile, _current_player, dir);
 		MarkTileDirtyByTile(tile);
 		MarkTileDirtyByTile(tile - delta);
 		MarkTileDirtyByTile(tile + delta);
@@ -161,6 +161,8 @@ static int32 RemoveShiplift(TileIndex ti
 {
 	TileIndexDiff delta = TileOffsByDir(GetLockDirection(tile));
 
+	if (!CheckTileOwnership(tile)) return CMD_ERROR;
+
 	// make sure no vehicle is on the tile.
 	if (!EnsureNoVehicle(tile) || !EnsureNoVehicle(tile + delta) || !EnsureNoVehicle(tile - delta))
 		return CMD_ERROR;
@@ -249,7 +251,11 @@ int32 CmdBuildCanal(TileIndex tile, uint
 		cost += ret;
 
 		if (flags & DC_EXEC) {
-			MakeWater(tile);
+			if (TileHeight(tile) == 0) {
+				MakeWater(tile);
+			} else {
+				MakeCanal(tile, _current_player);
+			}
 			MarkTileDirtyByTile(tile);
 			MarkTilesAroundDirty(tile);
 		}
@@ -279,6 +285,8 @@ static int32 ClearTile_Water(TileIndex t
 				return_cmd_error(STR_0002_TOO_CLOSE_TO_EDGE_OF_MAP);
 			}
 
+			if (GetTileOwner(tile) != OWNER_WATER && !CheckTileOwnership(tile)) return CMD_ERROR;
+
 			if (flags & DC_EXEC) DoClearSquare(tile);
 			return _price.clear_water;