 As with almost all of the estuarine system including the Bathurst Channel, the seabed falls sharply from the shore before hitting the level floor of the harbour which forms a gently sloping basin of mud and gravel with a maximum depth of near Dixon Island.Waters within a radius of the harbour entrance vary greatly in depth with three deep channels branching out from the entrance leaving deep shoals in between at a depth of .The true deepest point in the harbour is where the three channels meet between Platypus Point and Nixon Point which reaches due to the dredging action of the tide.