Altona Pier is the western suburbs' equivalent of the eastern bayside sand piers: a long timber structure over a gently shelving bottom that is more useful than exciting. It runs south from the foot of Pier Street across a clean sandy shallows that gives way to soft black muck toward the outer end, where depth reaches about 5 m. The pylons are thick with mussels and carry sea squirts, tubeworms and algae, and the marine life around them is limited and, in The Scuba Doctor's words, very skittish: puffers and toadfish, small leatherjackets, blennies, gobies, sea stars, sand crabs, the occasional seahorse or pipefish in the weed and an octopus or two under the debris, with a supermarket trolley at the end of the pier providing the traditional Port Phillip pier ornament.

Forty to sixty-five metres beyond the pier head an artificial reef has been placed on the sand; it is outside the 30 m no-spearfishing zone around the pier and is fished, and it draws a few more fish than the pier itself. The site's virtues are shelter from northerlies, a free car park, toilets, shops and a park with benches within a hundred metres, and the flattest, easiest conditions imaginable, which is why it is described as an excellent training ground for new divers close to the city and why it is a reasonable first night dive. For anyone else it is a snorkel or a last resort when the wind has south in it everywhere else.

The Seaholme boulder reef, 1.4 km east along the beach, is a better natural dive on the same stretch of shore.

Altona is 15 km south-west of the CBD via the West Gate Freeway and Millers Road, or by train to Altona station and a 400 m walk down Pier Street. The pier is at the foot of Pier Street; the foreshore car park is free but busy in summer, and the carry to the pier is under 100 m. Walk out along the pier to the lower landing and enter with a back roll or seated entry because the water is only a metre or two deep, or simply walk in from the beach beside the pier.

Note that the outer section of the pier has at times been closed for structural repairs with only the first 150 m open; check before planning to enter from the far landing. Exit at the landing or on the beach.

Best in north, north-east, north-west or west winds, or light south, south-west or east winds; the pier faces south and a fresh southerly or south-easterly puts chop along it and lifts the fine black silt. Dive at high tide for depth. Visibility 2-5 m at best, better in winter, poor after rain (Kororoit and Laverton creeks discharge nearby).

No swell. Suitable for day and night dives; probably better as a snorkel in daylight.

Enter at the lower landing, follow the pylons out to the end at about 4-5 m over the black silt, look for the artificial reef 40-65 m beyond the end if visibility allows (compass bearing straight out), return under the pier on the other side, and finish in the sandy shallows by the beach. Keep a metre off the bottom.

No regular commercial operator – dived independently and by western-suburbs dive clubs and Melbourne shop social dives; no shop is based in Williamstown, so fills come from Dive Victoria Group or Scuba Culture.