Blue Hole

The Blue Hole is a world-famous underwater sinkhole located at Lighthouse Reef Atoll, Belize, reaching a maximum depth of 113.6 m (373 ft). It was made famous by Jacques Cousteau and is a large marine cavern system characterised by stalactites, overhangs, and a deep cavern structure formed when sea levels were lower and the cave system was above water.

The terrain descends into an extensive cavern system with a sandy bottom at maximum depth. Stalactites hang from the cavern ceiling, evidence of its geological past as a dry limestone cave. A thermocline is present, and water circulation is poor at depth, leading to anoxic conditions in the deeper sections where sunlight is severely limited.

Marine life at the Blue Hole includes groupers, horse-eye jacks, squirrelfish, pompano, angelfish, and butterflyfish, along with Pederson's cleaning shrimp and neon gobies. The site is particularly known for shark encounters, with reef sharks, blacktip reef sharks, hammerhead sharks, tiger sharks, and lemon sharks all recorded here, with July through September considered a notable season for shark activity.