Hol Chan Marine Reserve sits on the barrier reef about 8 km south-southeast of Caye Caulker and is accessible by boat in around 25–30 minutes. The reserve has four zones, but most day-trippers visit Zone A (the reef cut, full of reef fish and coral formations) and Zone B (Shark Ray Alley, where nurse sharks and southern stingrays congregate in shallow water, fed for decades by tour boats).
Nearly all tour operators on Caye Caulker offer half-day snorkel trips combining Hol Chan and Shark Ray Alley (BZ$80–100 per person). The marine life is genuinely prolific — this is one of the better snorkeling sites on the Western Caribbean. Arrive early before the day-trip boats from Ambergris Caye crowd the site.