Tuna Hut is the second half of a typical West End day at Rottnest. Perth Scuba and Divernet describe it as a large site on the north-west of the island with caves and swim-throughs, lots of crayfish, and a seal colony nearby, noting that it makes a good dive shortly after Shark Cave and offers good photographic opportunities. The name presumably comes from an old fishing hut on the shore, a reminder that this part of Rottnest was once used by tuna fishers.

The reef is shallower than Shark Cave, which makes it a sensible second dive after the deeper shark site, and its limestone is eroded into the familiar Rottnest mix of overhangs, caves and swim-throughs. Western rock lobster are common in the cracks. With the seal and sea lion colony close by, there is a chance of a curious animal joining the dive, and the clearer offshore water at this end of the island gives good visibility.

Published detail about depths and layout is limited, so treat the depths given here as indicative and follow the charter's brief. It suits Open Water divers with some experience in surge and swim-throughs. Because it is only reachable on the handful of calm days each year when boats get to the West End, it is less dived than the north-east sites but well worth doing when the chance arises.

Combine it with a look at the seal colony from the boat, keeping a respectful distance from animals hauled out on the rocks.

Reached on West End charter days from Fremantle (about 1-1.5 hours) as the second dive after Shark Cave; private boats run along the north coast toward the West End. No moorings - live-boat or anchor on sand. Rottnest lies about 18 km west of Fremantle; allow 45-90 minutes each way by charter or trailer boat depending on the site.

Follow Rottnest Island Authority mooring and anchoring rules - do not anchor on reef or in sanctuary zones - carry a marine radio and log a trip plan, as the crossing of Gage Roads can turn rough when the afternoon sea breeze arrives.

Exposed north-west/West End site; needs low swell and light easterly winds, the same rare days that make Shark Cave possible (mostly summer and autumn). Sea breeze from late morning makes the run home rough. 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.

Drop on the reef, tour the caves and swim-throughs at 10-15 m looking for crayfish, then drift along the reef toward the seal colony area if sea lions are about, ascending on a DSMB. Agree a turn pressure before descending (half gas, or a third where current is likely), carry a DSMB, and make a 3-minute safety stop at 5 m.

Perth Scuba uses it as the follow-up dive on West End trips after Shark Cave when conditions allow. Nearest dive services: Perth Scuba, Bucket List Diver and Dolphin Scuba (Perth/Fremantle) run Rottnest boat trips; there are no dive shops or air fills on the island.