The Great Blue Hole is a near-perfectly circular sinkhole about 300 m across, plunging roughly 124 m into the seabed at Lighthouse Reef atoll off Belize. Toggle the depth bands to see the color-coded drop from turquoise reef to navy depths, and the stalactite-ledge marker to see the overhang left from when this was a dry cave.
Published figures: diameter about 300 m (984 ft); depth about 124 m (407 ft); shape a near-perfect circle; location Lighthouse Reef atoll, Belize, Caribbean Sea; part of the Belize Barrier Reef Reserve System, a UNESCO World Heritage Site since 1996; underwater stalactites documented on overhangs around 40-50 m depth, evidence it was once a dry, air-filled cave.
Drag to orbit and scroll or pinch to zoom. Everything renders on your device with WebGL.
Great Blue Hole 3D Explorer
This browser explorer shows the Great Blue Hole as a cross-section: shallow turquoise reef flat surrounding a near-vertical shaft that drops into deep navy water, at Lighthouse Reef atoll off the coast of Belize in the Caribbean Sea.
The hole formed as a limestone cave during past ice ages, when sea level was much lower and the area was dry land. As the cave's ceiling eroded and collapsed and the sea rose after the ice age, it flooded into the near-perfectly circular, steep-walled sinkhole seen today. Divers have documented limestone stalactites hanging from overhangs around 40-50 m depth - formations that only form in air, confirming the hole was once an open, dry cave before the sea reclaimed it. The site was popularized worldwide after Jacques Cousteau surveyed it in 1971 and named it one of the top diving sites on Earth.
- Toggle depth bands to see the color-coded drop from reef to the deep floor
- Toggle the stalactite-ledge marker to see the ancient cave overhang around 40-50 m down
- Read diameter, depth, and formation history in the panel
- Drag to orbit, scroll or pinch to zoom
- Runs fully in the browser with the vendored three.js engine - no account, no upload
- Your depth-band and ledge-marker choices are saved in your browser, so the scene reopens the way you last left it
| Figure | Published value |
|---|---|
| Diameter | about 300 m (984 ft) |
| Depth | about 124 m (407 ft) |
| Shape | near-perfect circle |
| Stalactite ledges | documented on overhangs around 40-50 m depth |
| Formation | collapsed limestone cave, flooded as sea level rose after the last ice age |
| Location | Lighthouse Reef atoll, Belize, Caribbean Sea - part of the Belize Barrier Reef Reserve System, UNESCO World Heritage Site since 1996 |
For another near-perfect natural circle shaped by water and geology, see the Dead Sea 3D Explorer, or for a different kind of extreme underwater depth, the Mariana Trench 3D Explorer.
The Great Blue Hole relief and its stalactite-ledge ring are built and rendered on your own device with WebGL, so orbiting the ~124 m shaft and flipping the depth bands stays smooth after the vendored three.js engine loads once (about 0.7 MB) and is cached for return visits.
Reading the depth bands
Two toggles carry most of the teaching value here. The depth-band coloring maps the color-coded drop from the turquoise reef flat to the deep navy floor, so the roughly 124 m plunge reads at a glance instead of as a flat number, and the stalactite-ledge marker pinpoints where divers document limestone overhangs around 40-50 m down - the tell that this sinkhole was a dry, air-filled cave before the sea flooded it. Drag to orbit, scroll to zoom, and your toggle choices are saved in browser storage so the scene reopens the way you last left it.
This is an educational approximation - the reef texture, wall profile, and stalactite placement are schematic teaching cues, not a survey-grade bathymetric model.
Frequently Asked Questions
How big is the Great Blue Hole?
About 300 m (984 ft) across in a near-perfect circle, and about 124 m (407 ft) deep.
How did it form?
It was a limestone cave on dry land during the last ice age, when sea level was much lower. As the ice age ended and the sea rose, the cave's roof collapsed and flooded, leaving the steep-walled circular sinkhole seen today.
What are the stalactites doing underwater?
Divers have documented limestone stalactites hanging from overhangs around 40-50 m depth. Stalactites only form in air, so their presence underwater confirms the hole was once a dry, air-filled cave before the sea reclaimed it.
Where is the Great Blue Hole?
At Lighthouse Reef atoll off the coast of Belize, in the Caribbean Sea, part of the Belize Barrier Reef Reserve System - a UNESCO World Heritage Site since 1996.
Why is it famous?
Jacques Cousteau surveyed it in 1971 and named it one of the top diving sites on Earth, drawing worldwide attention to the site.
Is this a scientific bathymetric model?
No. It is an educational explorer using published figures - the reef texture, wall profile, and stalactite placement are schematic teaching cues, not a survey-grade model.