Cowes Jetty is Phillip Island's town pier, a long timber structure running north from the foot of Thompson Avenue into Western Port, and it is the island's most convenient and most frequently dived shore site. Scuba Doctor lists it at 2–15 m, recommends it for night dives, and notes the sheltered beaches, toilets, barbecues and playgrounds around it – this is a dive done from a car parked on The Esplanade with a cafe a hundred metres away. The pier is used by the Western Port passenger ferry from Stony Point and by seasonal cruise boats, and the dive is a classic pylon crawl: out along one side, back along the other, in the sand and seagrass shallows near shore and deeper water towards the head.

The pylons carry the mixed growth typical of Western Port piers – sponges, ascidians, hydroids, tubeworms and mussels – and among them live the animals that make Victorian pier diving what it is: big-belly seahorses, pipefish, decorator crabs, spider crabs (in large aggregations some winters), hermit crabs, cowfish, globefish, nudibranchs and octopus, with leatherjackets, wrasse and juvenile fish schooling in the shade of the deck. On the sand and seagrass beside the pier are stingarees, fiddler rays, flathead and goatfish, and at night the pylons come alive with crabs, shrimp, squid and hunting octopus. The bottom is scattered with fishing debris and the odd historical relic.

Visibility is Western Port visibility – rarely more than 8 m, sometimes much less – and the tide runs along the pier, so timing for slack or the flood matters. The wreck of the steam launch Vixen lies 450 m to the west and is a separate dive. Cowes Jetty suits any certified diver in reasonable conditions, is the natural place for a night dive or a check-out after a lay-off, and is the fallback for visitors when the ocean coast is unworkable.

Its weaknesses are ferry traffic, fishing line and modest clarity; its strength is that it is always there.

Cowes is the main town on Phillip Island, 140 km (about 2 hours) from Melbourne; the jetty is at the bottom of Thompson Avenue where it meets The Esplanade, at the corner of Bass Avenue. Park along the northern side of The Esplanade east of the jetty (time limits apply in summer) – it is a 50–100 m carry to the beach. Enter from the sand at the head of the pier on the eastern side and swim out along the pylons; the outer end is about 300 m offshore, so many divers fin out on the surface and descend near the ferry landing.

Stay clear of the ferry berth when the Western Port Ferries service is arriving or departing.

The jetty faces north into Western Port, so it is sheltered from the prevailing south-westerly and, per Scuba Doctor, best during calm seas with offshore southerly winds; strong northerlies push chop and weed onto the beach and make it unsuitable. Tidal variation is significant and the current along the pier is noticeable, so dive at slack water or on the incoming tide, which also brings clearer water in from the entrance. Visibility is modest and drops after rain and northerly blows.

Diveable year-round and one of the island's most reliable options; a popular night dive.

Enter on the eastern side of the pier head, swim out along the pylons on the surface or at 2–4 m and descend fully at the deeper section towards the ferry landing, working the pylons out to the end in 6–8 m (the deeper channel beyond reaches 15 m). Return along the opposite side of the pier, staying under the deck and away from the ferry berth, and exit onto the beach. At night, follow the same route with a torch and a shore marker light.

No dive shop or dedicated dive charter is based on Phillip Island. Sites are dived by Melbourne clubs (VSAG, Melbourne University Underwater Club, Frankston/Peninsula clubs) and private boats launched at Newhaven or Rhyll; Mornington Peninsula shops (Dive Victoria Group, Portsea; The Scuba Doctor, Rye) run occasional Phillip Island days. Ocean Adventures Phillip Island (Cowes) runs seal-snorkel tours only.

Cowes Jetty is the island's standard night dive and is used by clubs and visiting groups.