St John Caves

The dive drops off the zodiac and descends a sloping reef to an opening on the southern face, then works a slow looping route that uses the shafts of daylight as the navigation cue. The roof is rarely far above and there is always an exit in sight, which is exactly why this stays a guided daylight cavern rather than a true overhead, and why good buoyancy, not depth or current, is the skill that matters. Inside, the walls and ceilings carry soft corals and sponges. Clouds of glassfish and sweepers mass under every opening, and a torch picks ghost pipefish, nudibranchs, shrimp and the odd giant moray out of the crevices.

Outside the arches the coral garden runs with anthias, butterflyfish, parrotfish and wrasse, with a Napoleon wrasse cruising the edges and blue-spotted stingrays on the sand. The whole route is shallow enough that 60-minute dives are routine and Nitrox extends bottom time without depth pressure. Returns are by zodiac pick-up, and an SMB is standard because multiple liveaboards stack up here at peak times. It is a slow, contemplative dive: divers chasing pelagics come away flat, while those who came for topography and light call it the highlight of the trip.

St John's Caves is a cathedral of light rather than a thrill dive. Three things set it apart from the rest of the cluster. The depth is the first: a 3-12 metre cavern top means hour-plus dives on Nitrox and ambient light strong enough to shoot wide without heavy strobes. The topography is the second: arches, swim-throughs and tunnels are stacked into one site rather than spread across an itinerary, so a single dive delivers the whole cavern format. Accessibility is the third. In an area whose habili walls demand Advanced training and current discipline, this is the dive nearly everyone on the boat can do.

It is also a coral-architecture dive in a year when coral is the story. As of 2025-2026 the Deep South is living through a regional bleaching event, and recent divers note bleached patches alongside the intact structures. The light, the swim-throughs and the glassfish still carry the dive, and the clarity that makes the shafts work is one of St John's genuine strengths. This is the gentle counterweight to the shark pinnacles, the afternoon dive after the morning walls.

Bring both lenses across the day. Wide-angle is the obvious call for the light beams and the cavern interiors, shot toward the openings so the shafts and the glassfish silhouette against the blue. The shallow profile and strong ambient light mean you can work without heavy strobes, which is part of why the site has its photographer's reputation. Macro pays off in the crevices, where a torch turns up ghost pipefish, nudibranchs, shrimp and small morays, so many shooters carry each rig on a different dive.

Timing and trim are everything. Run the cavern in the afternoon when the sun is highest and the shafts are strongest, and get into the water early in the rotation before fins stir the silt. A buoyancy error clouds the interior fast and ruins the frame for everyone behind you, so hover, keep off the coral, and let the guide set the pace through the arches. The light moves as you move, so it rewards patience over a fast lap.

Treat the cavern as an overhead, even though it is shallow and forgiving. Stay with the guide, keep exits in sight, and do not push beyond the natural-light zone or your certification. The main skill is buoyancy and no-contact control: hover, don't settle, and keep your fins clear of the floor, because one careless kick silts the interior and degrades both the dive and the photographs. Carry a torch for the darker pockets even in a daylit cavern, and an SMB for every ascent, since boat traffic at the moorings is the main surface hazard.

This is remote, expedition diving. The cavern is the accessible dive of a Deep South liveaboard trip, but the trip itself is a long southern crossing to uninhabited reefs, usually a 7-night route paired with Fury Shoals and Sha'ab Sataya. The nearest recompression chamber is around 200 kilometres away at Marsa Alam, so dive conservative profiles and carry DAN-style insurance. Nitrox is worth taking for the long, shallow days.