Salmon Bay is the bigger sibling of Little Salmon Bay on Rottnest's south coast. Marinelife.org.au describes it as a protected bay 4.5 km from the ferry terminal with shallow reef (2-3 m) and large sandy expanses, corals on limestone ledges and lots of small marine life, best reached by bicycle and excellent for beginners. SeaLink's guide calls it larger and more exposed, with extensive reef systems, schools of black bream, dusky morwong and abundant coral, and recommends it for more adventurous snorkellers.

The difference in these descriptions reflects the weather: in easterly winds the bay is calm and clear and very easy, while southerly weather makes it choppy and surgy. The Rottnest Island Authority's warm-water guide groups Salmon Bay with Parker Point as the island's tropical-fish hotspot, with some 135 tropical species and a range of coral forms supported by the Leeuwin Current.

The bay suits snorkellers and scuba divers who want more space than Little Salmon Bay offers. Offshore, the south coast deepens toward sites such as Jack's Patch and the Salmon Bay unidentified wreck, which need a boat. Check the wind before cycling out: if it is from the south, go to the north-coast bays instead.

There are no shops at the bay, so bring water and sun protection, and plan the ride back into the afternoon sea breeze.

Rottnest's south coast is where the warm Leeuwin Current has most influence, which is why the corals and tropical fish in these bays are unusual for a location so far south. The Rottnest Island Reserve bans spearguns and handspears across all island waters. The general rule is simple: in a northerly or easterly, snorkel the south side; in a southerly, go to the north-coast bays instead.

Cycle about 4.5-6 km from the Thomson Bay settlement along the south coast road (marinelife.org.au recommends a bicycle) or take the Island Explorer bus. Park bikes above the beach and walk down to the sand. Enter from the beach; the reef is close to shore.

Snorkel gear can be hired in the settlement; scuba divers must bring filled cylinders from Perth on the ferry, as there are no fills on the island.

SeaLink lists north, north-east, east and south-east winds as suitable. Salmon Bay is larger and more exposed than Little Salmon Bay and becomes rough with southerly and south-westerly winds and swell. Calm summer mornings with easterlies are ideal.

General pattern at Rottnest: summer brings calm morning easterlies followed by a strong south-westerly sea breeze from late morning, so dive early; winter brings north-westerly fronts and large swell, with clear, calm spells between them. Check the Bureau of Meteorology coastal forecast for swell height and period before committing.

Enter from the beach and snorkel along the shallow reef ledges, looking under them for corals and small fish, then cross the sand to the next patch of reef; return along the shore. Snorkellers should stay within easy reach of the exit point and swim with a buddy; scuba divers at these depths need no safety stop but should ascend slowly and surface near the float.

No operator needed - self-guided snorkel/shore dive. Snorkel gear hire from Pedal & Flipper and other outlets in the Thomson Bay settlement; guided snorkel tours (Rottnest Snorkel) run from Thomson Bay. Scuba divers bring cylinders from Perth - no fills on the island.