Cato Reef lies in the far south of the Coral Sea Islands Territory, roughly 100–120 km south of Wreck Reefs and around 500 km off the Queensland coast. Reef Life Survey, which visited on the vessel Reef Dragon from Mooloolaba after a crossing of about 40 hours, describes calm water with 40 m-plus visibility, flat reef areas around 10–15 m deep, giant coral bommies reaching to the surface and lagoon habitats, with a diverse range of fish and invertebrates. The 15-hectare coral cay supports seabirds.

The layout offers straightforward diving by Coral Sea standards: broad reef flats at moderate depth, punctuated by bommies that rise to the surface, and sheltered lagoon areas. In clear, calm conditions this is excellent diving, with long bottom times and the chance to see the reef's full structure.

The survey did not list species for Cato specifically, but at nearby Wreck Reef the same team recorded whitetip and grey reef sharks, black snapper, humpnose unicornfish, Maori wrasse, parrotfish, groupers, tuna, rainbow runner, marlin, Queensland groper and sea snakes, and similar fauna can be expected. The southern Coral Sea is subtropical, so water is a little cooler than on the northern reefs, especially in winter.

Cato is visited only by research voyages and occasional private vessels. It suits self-sufficient divers on capable boats.

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. Reef Life Survey reached Cato Reef on the vessel Reef Dragon from Mooloolaba after a crossing of about 40 hours.

Anchor in the lee of the cay in calm weather. 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 the flat reef areas at 10–15 m and the giant bommies that rise to the surface, circling each bommie and finishing on its top. Lagoon habitats offer sheltered alternatives.

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