Portsea Hole

Portsea Hole
Portsea Hole, located off the coast of Victoria, Australia
Location	Port Phillip Heads Marine National Park, Port Phillip, Victoria
Coordinates	38°18′39″S 144°42′40″E / 38.3109°S 144.7111°E / -38.3109; 144.7111Coordinates: 38°18′39″S 144°42′40″E / 38.3109°S 144.7111°E / -38.3109; 144.7111
Elevation	descends 20–32 m (66–105 ft)
Length	400 metres (1,300 ft)
Width	250 metres (820 ft)
Area	10 hectares (25 acres)
Operator	Parks Victoria
Designation	IUCN II – marine park
Website	Portsea Hole at Parks Victoria

The Portsea Hole is a depression in the seafloor of Port Phillip near Portsea in Victoria, Australia. The undefined area of the depression, generally assessed at 10 hectares (25 acres), is one of six separate areas that comprise the Port Phillip Heads Marine National Park and is a popular site for divers.

The Portsea Hole is a remnant section of the drowned valley of the Yarra River, descending sharply from the 12 metres (39 ft) depth of the surrounding seabed to 32 metres (105 ft), exposing changes in the strata of the limestone sides with depth. It is characterized by diverse and abundant fish assemblages as well as a rich benthic community of marine invertebrates, encrusting algae, sponges and soft corals.