The Great Blue Hole

The Great Blue Hole of Belize is one of the world's most iconic underwater features — a perfectly circular 305-meter-wide karstic sinkhole 124 meters deep at the heart of Lighthouse Reef, 60 kilometers off the Belize mainland. Famously explored by Jacques Cousteau in 1971 (who ranked it among his top-ten dive sites globally) and visible from space as a dark blue disc set in the turquoise Caribbean, it is Belize's single most celebrated dive destination and a bucket-list target for serious divers worldwide. The dive is a vertical descent inside the sinkhole to 40 meters, where divers encounter the prehistoric limestone stalactites that define the site — enormous geological formations hanging from overhangs that formed when the cave system was above sea level during the Pleistocene era, more than 10,000 years ago. Some stalactites extend several meters from the ceiling, creating a surreal landscape that evokes terrestrial caves more than any ordinary dive. Recent sonar surveys have also revealed features at the sinkhole's bottom, though these are accessible only by technical submarine expeditions. Shark encounters are a defining feature. Caribbean reef sharks cruise the blue water of the sinkhole's interior, and black-tip reef sharks and the occasional bull shark or hammerhead have been recorded. Midnight parrotfish and large groupers patrol the wall at depth. The surrounding reef, by contrast, hosts the full Caribbean complement — nurse sharks, eagle rays, sea turtles, and an exceptional diversity of reef fish. The Great Blue Hole is Advanced Open Water diving with strict bottom-time limits (typically 8 minutes at 40 meters). Reached exclusively from day boats departing Ambergris Caye or Caye Caulker (2-3 hours each way) or as a fixed stop on Belize liveaboard itineraries. Most operators pair the Blue Hole with two shallower Lighthouse Reef dives on the same day trip. Visibility inside the hole 30-40 meters, on the reefs 20-30 meters. Water temperatures 26-29°C. Best conditions April through June.