Mary's Place is the most-talked-about dive site on Roatán: a series of deep volcanic fissures cutting through the reef wall on the island's south side, near French Harbour. The fissures run from about 18 to 38 metres, narrow enough in places that two divers can only just fit side by side. Inside the cracks are sea fans, sponges, the occasional reef shark, and very large numbers of silversides.
Mary's Place is in a marine reserve and limited to ten dive boats per day; book through any dive shop. It is an advanced site (depth, swim-throughs) but not technical — Open Water divers with some experience handle it routinely.