Wall dive

A dive along a vertical or near-vertical reef face dropping into deep water, with the wall on one shoulder and open blue on the other.

A wall dive follows a vertical or near-vertical underwater cliff, typically the outer face of a reef where the bottom plunges from a shallow rim into hundreds of meters. You swim with the wall on one shoulder and open blue water on the other, an experience closer to flying along a cliff face than swimming over a seabed. Little Cayman's Bloody Bay Wall and Bunaken in Indonesia are benchmark examples.

Walls concentrate life because current pushes food along the face: sea fans, sponges, and whip corals crowd the structure, while sharks, turtles, and schooling pelagics pass in the blue. Navigation is the easiest in diving, wall on the left going out, wall on the right coming back, but depth control is the hardest, because there is no bottom to stop a slow sink while your attention is on the reef.

Plan a hard maximum depth, level off, and check your gauge and no-decompression limit frequently. Watch for downcurrents where flow bends over the rim, and finish the dive working up the wall so the safety stop happens against the shallow reef rather than in featureless blue. A dive light reveals the true colors of the sponges and fans that make walls famous.