Great Blue Hole Diving: What to Expect on Belize's Most Famous Dive

Diver with a torch exploring a dark underwater cave, like the stalactite ledges of the Great Blue Hole

Great Blue Hole diving is the dive most visitors to Belize have heard of before they arrive. The giant circle of deep blue in the middle of Lighthouse Reef appears in countless aerial photos, and a dive there takes you down a sheer limestone wall to ledges hung with stalactites that formed when the cave was dry land. This post explains what the dive is really like, who it suits and how to plan the day.

What the Great Blue Hole Is

The Great Blue Hole is a marine sinkhole about 300 metres (roughly 1,000 feet) across and well over 100 metres deep. It formed during past ice ages, when sea levels were much lower and the area was a limestone cave system on land. As the ice melted and the sea rose, the cave roof collapsed and the hole flooded. The stalactites you see on the dive are the evidence: they can only grow in air.

The hole was made famous by Jacques Cousteau, who brought his ship Calypso here in 1971 and declared it one of the top dive sites in the world. Today it is protected as the Blue Hole Natural Monument, managed by the Belize Audubon Society, and it is part of the Belize Barrier Reef Reserve System, a UNESCO World Heritage Site.

What the Dive Is Like

The typical Blue Hole dive is short and deep. You descend over the rim, where the reef gives way to a sandy slope, then drop down the wall to around 40 metres (130 feet), the usual limit for recreational divers. At that depth the wall cuts back under an overhang, and huge stalactites hang in the gloom. You spend only a few minutes there before a slow ascent along the wall and a long safety stop near the rim.

Caribbean reef sharks often patrol the deep water, and you may see groupers and other large fish around the rim. Below about 15 metres the light fades and the colour drops away, so this is a dive about scale and geology rather than coral. Some divers find it breathtaking; others prefer the reef dives that follow. Most agree it is worth doing once.

Who Should Do It

Because the dive goes to around 40 metres, many operators ask for an advanced certification, a deep specialty or recent deep-dive experience, and some check your logbook. Even if a shop will take newer divers, you will enjoy it more if you are comfortable with buoyancy control, equalizing quickly and managing your air at depth. If you are not there yet, consider doing an Advanced Open Water course early in your trip. Our guide to Belize dive shops covers what to ask about training and group size.

A dive computer is essential, and a torch helps you see the stalactites. See our scuba diving gear guide for Belize for the details.

How the Day Works

Lighthouse Reef is the most distant of Belize's three atolls. From Ambergris Caye or Caye Caulker the boat ride takes two hours or more each way, and seas outside the barrier reef can be rough, so take seasickness precautions if you need them. A typical trip includes:

An early start, often before sunrise, with breakfast on the boat or before you leave.
The Blue Hole dive first, while you are fresh and before the surface interval clock starts.
A second dive on the walls of Lighthouse Reef, which are full of coral and fish.
Lunch and a stop at Half Moon Caye Natural Monument, known for its colony of red-footed boobies.
A third shallower reef dive before the long ride home.

Marine park fees for the Blue Hole and Half Moon Caye are usually extra or bundled into the trip price, so ask when you book. Weather cancels trips, so schedule the Blue Hole early in your stay to leave spare days.

Staying Closer: Atoll Lodges and Liveaboards

If you want to dive Lighthouse Reef without the long daily ride, stay on the atoll itself or join a liveaboard. Atoll lodges and liveaboards usually run the Blue Hole at a calmer hour and combine it with several days on the outer walls. Our Belize dive accommodations guide compares the options, and the post on Belize's three atolls explains how Lighthouse Reef compares with Turneffe and Glover's Reef.

Safety Tips for a Deep Dive

Follow the guide's plan for depth and time, and do not chase the wall deeper.
Watch your no-decompression time on your computer; it runs down fast at 40 metres.
Ascend slowly along the wall and complete a full safety stop.
Be well rested and hydrated, and skip alcohol the night before.
Leave at least 18 hours after a multi-dive day before flying, as Divers Alert Network recommends.

Planning the rest of the trip? Start with our Belize dive travel guide.