St John Caves

Shallow cracks in the reef plate open into caverns and overhangs, and slivers of sunlight filter down into the tunnels, so the route is a string of bright rooms joined by coral-covered passages. Between the swim-throughs, patches of sand hold blue-spotted rays, and the walls and rocks hide ghost pipefish, nudibranchs and shrimp for anyone willing to look closely.

Depth runs 5 to 20 m on one operator's account, and the ambient light is strong enough for wide-angle frames without a battery of strobes. Outside the caves the coral gardens carry anthias, butterflyfish and groupers, and larger fish such as barracuda and trevally cruise off the reef, with a giant Napoleon wrasse among the regulars. A 2005 dive log here records 16 m maximum depth over 62 minutes.

The caves are a maze of shallow caves, swim-throughs and coral-covered tunnels lit by daylight through the openings. Visitors on St John's trips describe the caverns as beautiful, and operators say the site suits both thrill-seekers and those who like slow, detailed exploration.

The reef itself has taken a knock. Divers in late 2025 report coral bleached in many places across the St John's reefs, and some find less marine life than they hoped for and busy moorings.

Hard coral and sharp rocks surround the caverns and swim-throughs, and stirred sediment damages the coral and clouds the water for everyone behind you. An SMB is a must, with so many boats around these popular sites. St John's is reached by liveaboard, an overnight sail of around 14 hours from Port Ghalib, and groups are ferried to the reef by tender. Keep your fins off the floor and your hands off the coral at every opening, because the caves leave no room to correct a buoyancy error.