The Willis Islets are a sunken atoll roughly 45 by 19 km in the central Coral Sea with three islets. Marinelife.org.au notes that the lagoon is about 8 m deep and that Willis Island is the only inhabited island in the Coral Sea, home to a Bureau of Meteorology weather station established in 1921. The station is an important early-warning post for cyclones approaching the Queensland coast.

Diving here is incidental to expeditions and research voyages rather than a destination in itself, and no dive sites are named in the sources consulted. The shallow lagoon offers sheltered diving and snorkelling over coral and sand at around 8 m, while the outer slopes of the atoll drop into deep water and can be dived in calm weather. Visibility on the outer reef is typically excellent.

The islets are important seabird habitat, and Parks Australia's recent protection measures for Coral Sea islands mention seabird colonies, including sooty terns, brown noddies and shearwaters, on South and Bird islets. Green turtles are likely to nest on the islets as they do elsewhere in the Coral Sea. Expect the typical fauna of remote Coral Sea reefs: reef sharks, groupers, trevally, parrotfish and turtles.

Willis suits self-sufficient expedition divers. Visitors must follow the Parks Australia island access guideline and must not land on the weather-station island without permission. It is best treated as a stop on a longer expedition rather than a dive destination. Because the atoll is in the path of cyclones, trips are best planned for the calmer months of September to December.

There is no scheduled dive operator. Access is by private expedition charter, research voyage or cruising yacht with Coral Sea experience, self-sufficient for several days and carrying compressor, oxygen and satellite communications. Willis Island is about 450 km east of Cairns, roughly two days' passage.

The lagoon is about 8 m deep. Landing on the weather-station island requires Bureau of Meteorology permission, and some islets are closed to protect seabirds. Commercial tours need Parks Australia authorisation, and some islands are closed to landing.

These are remote oceanic reefs with no shelter from the south-east trades beyond their own reef rims, which blow 15–25 knots for much of April to October and make the multi-day open-ocean passage rough. Expeditions target calm windows, most often September to December; the lagoon anchorages give protection in moderate trades but the outer walls are dived only in light winds. December to April is cyclone season and trips are rarely scheduled then.

Currents on the walls and through passes can be strong; visibility is usually 30 m or more.

Dive or snorkel the lagoon at around 8 m in trade-wind weather; outer-reef slopes only in calm conditions with tender cover.

No regular operator – occasional private expedition charters, research voyages and cruising yachts only; any commercial tour requires Parks Australia authorisation.