When encountering a dredge vessel recreational boat operators should always maintain a safe speed and pass on the non obstruction side of the dredge vessel. The safe side of passage is indicated by a double black diamond signal on the vessel. A double black ball signal indicates the obstruction side to avoid. A third black ball, black diamond, black ball signal indicates the vessel is restricted in its manoeuvrability.
Maintenance dredging is conducted by Parks Victoria to maintain safe access to boating facilities in key locations such as Queenscliff, Patterson River, Werribee River, St Kilda Pier and Mordialloc Creek. Water depth surveys are also available for Patterson River and Mordialloc Creek.