St Kilda Pier is Melbourne's best-known pier and one of its more interesting inner-city dives, mostly because of the seagrass. The pier began as a working jetty in the mid-1800s and juts west from the St Kilda foreshore; the rock breakwater on its southern side was built for the 1956 Olympic sailing events and still shelters the harbour, with the original race start tower in use. The breakwater is now home to a colony of little penguins and a rakali population and is off limits to divers, and the marina behind it is busy, so the dive is confined to the open northern side and the head of the pier.

That side is fringed by extensive Zostera and Heterozostera seagrass meadows, which act as a nursery: juvenile fish, pipefish, seahorses, gobies, cuttlefish and southern calamari eggs are all found in the weed, and at night the meadows come alive with octopus, dumpling squid and stingarees. The pylons themselves carry mussels, sea squirts and sponges with blennies, cardinalfish, leatherjackets and sea stars, and on the sand between the weed you may see fiddler rays and flathead. Depth grows from 2 m off the beach to about 8 m at the head, which makes it slightly deeper than the other inner piers.

Visibility is the limiting factor: the Yarra and stormwater plumes keep it modest, and silt is easy to stir. It suits new divers, snorkellers, night divers and photographers who like seagrass macro, and it is the only pier in Melbourne you can reach by tram. Point Ormond Reef at Elwood is 2 km south for a second shallow dive.

St Kilda is 6 km south of the CBD via St Kilda Road or Beaconsfield Parade; trams 16 and 96 stop at the pier. Parking is metered along Jacka Boulevard and in the foreshore car parks and is very difficult on summer weekends, so dive early, midweek or at night. Walk down to the beach on the northern side of the pier (the open Port Phillip side) and gear up on the sand; the carry from the car parks is 100-200 m.

Enter from the beach and swim out along the pylons; do not enter within the marina or from the breakwater rocks, which are a penguin colony and a no-go area. Exit the same beach. Note the pier was rebuilt in 2023-24 and the landward section is now a wide concrete structure.

The pier points west so it takes wind chop from the west and south-west and is uncomfortable in anything above a moderate onshore breeze; easterlies and northerlies flatten it. Visibility is typically poor to moderate (2-5 m) and is best on the high tide and in winter; it deteriorates for days after rain. No swell.

Boat and jet-ski traffic in and out of the harbour is heavy on summer weekends, so a flag is essential and early mornings are best. Night dives are good, but stay away from the breakwater because of the penguins.

Enter from the northern beach, surface swim out to about 3 m, descend and follow the pylons seaward over the seagrass to the outer section (6-8 m), work around the head of the pier, then return under the deck on the same side. Do not cross to the marina side or approach the breakwater. Turn at half gas and finish in the seagrass shallows by the beach.

No regular commercial operator – dived independently and by Melbourne dive clubs and shop social-dive programs (Scuba Culture, Aquability, Melbourne Diving Services run occasional shore-dive nights at bayside piers); Ricketts Point-based snorkel tours run separately.