San Juan

San Juan is a reef dive site located in the north of Cozumel, within the Cozumel National Marine Park, and is rarely visited compared to other sites on the island. It is a flat strip reef with sand that slopes toward a drop-off. The terrain is dominated by large finger coral, lettuce coral, and sponges, with a few ledges and overhangs along the reef structure.

Depth runs 40–50 feet (12–15 m) on the main reef, with the option to go deeper toward the drop-off. The ledges and overhangs shelter French grunts and schoolmasters, while thousands of damselfish and red seaweed are found along the reef line. The site's primary draw is the possibility of encountering large pelagics, including barracuda, jacks, eagle rays, turtles, and sharks.

Conditions at San Juan are challenging: strong currents are expected, and the surface is typically windy with chop. Visibility and overall conditions improve notably when the sea is calm. The strong current makes photography of marine life particularly difficult. The site is rated advanced and is not suitable for less experienced divers. It is commonly done as a second dive, following a dive at Barracuda or Cantrel. As an extended-range northern site, it is selected based on weather, current, and diver experience on the day, and requires favorable sea conditions before it is attempted.