Seaholme Reef, also known locally as Wise's Reef, is a field of big basalt boulders lying close inshore off the Seaholme foreshore, a kilometre and a half east of Altona Pier. It is one of the few pieces of natural hard bottom on this stretch of the western shore and, being rarely dived, it is poorly documented; The Scuba Doctor lists it with an approximate position, a 2-5 m depth range and a note about the many big boulders, and this description is built from that and the character of the neighbouring basalt reefs at Williamstown and Point Cook. The boulders sit on sand and silt in 2-5 m and provide what the pier lacks: overhangs, gaps and shaded undersides.

On the western shore that habitat means encrusting sponges, tubeworms and mussels on the rock, common sea urchins, cushion stars, crabs and nudibranchs in the gaps, blennies, gobies, cardinalfish and small leatherjackets around the boulders, octopus and blue-ringed octopus underneath them, and stingarees, fiddler rays and flathead on the sand between. Seagrass patches nearby are worth checking for pipefish and seahorses. It is a shallow, easy shore dive with a sandy entry, suitable for new divers and snorkellers on a calm day with the wind in the north, and a plausible night dive for locals.

Its limitations are visibility, which is modest and collapses after rain because of Kororoit Creek, and the lack of any facilities beyond roadside parking. It is best thought of as the natural-reef companion to Altona Pier for divers who live in the west and want somewhere other than pylons.

From Altona Pier follow the Esplanade east toward Seaholme; park on the Esplanade or in the side streets near the Seaholme foreshore reserve (free, roadside). Walk 50-100 m across the beach and enter from the sand opposite the reef, which lies a short swim offshore. The position is given by The Scuba Doctor from Google Earth, so use the boulder patches visible from shore at low tide as a guide.

Exit on the same beach. Altona station is about 1 km away for those coming by train.

Like Altona Pier the reef faces south and is exposed to southerly and south-easterly chop; dive it in northerly through westerly winds or light southerlies, at high tide, and after a few dry days, because Kororoit Creek discharges just to the east and visibility falls sharply after rain. Visibility 2-5 m, best in winter. No swell.

Enter from the beach, fin out to the first boulders, descend at 2 m and work seaward and along the boulder line at 3-5 m, looking under the big rocks, turn at half gas and return on a reciprocal bearing to the beach.

No regular operator – dived independently by western-suburbs locals.