diff --git a/src/water_map.h b/src/water_map.h
--- a/src/water_map.h
+++ b/src/water_map.h
@@ -85,6 +85,11 @@ static inline DiagDirection GetShipDepot
 	return XYNSToDiagDir(GetShipDepotAxis(t), GB(_m[t].m5, 0, 1));
 }
 
+static inline Owner GetShipDepotWaterOwner(TileIndex t)
+{
+	return (Owner)_m[t].m4;
+}
+
 static inline DiagDirection GetLockDirection(TileIndex t)
 {
 	return (DiagDirection)GB(_m[t].m5, 0, 2);
@@ -128,13 +133,13 @@ static inline void MakeCanal(TileIndex t
 	_m[t].m5 = 0;
 }
 
-static inline void MakeShipDepot(TileIndex t, Owner o, DepotPart base, Axis a)
+static inline void MakeShipDepot(TileIndex t, Owner o, DepotPart base, Axis a, Owner original_owner)
 {
 	SetTileType(t, MP_WATER);
 	SetTileOwner(t, o);
 	_m[t].m2 = 0;
 	_m[t].m3 = 0;
-	_m[t].m4 = 0;
+	_m[t].m4 = original_owner;
 	_m[t].m5 = base + a * 2;
 }