Great Blue Hole
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40 free Great Blue Hole trivia questions with answers — geography quiz, new questions added Oct 2026.
Seen from the air, the Great Blue Hole is a dark circle punched into the pale shallows off Belize, and it looks like nothing else on Earth. It is also a time capsule: a drowned sinkhole whose walls and mud hold clues to vanished coastlines, old storms and the people who once lived nearby. This quiz collects the best fun facts about the Great Blue Hole and about blue holes in general. You will meet the explorers and submarines that went down into it, the wildlife around its rim, the science of why these pits form and why they look so dark, and the rival holes elsewhere that are deeper, deadlier or simply stranger. It suits divers, geography fans, students working on a project and anyone planning a trip. Every question comes with a short explanation, so you learn the story behind each answer as you play.
30 of 40 questions with answers and explanations. Play the quiz
Q 01Which undersea filmmaker made the Great Blue Hole famous when he explored it in 1971?
Jacques Cousteau
Jacques Cousteau sailed his research ship to Belize to chart the sinkhole's depths, and his team showed that it had once been a cave standing above the waves.
Q 02What did divers retrieve from caves inside the Great Blue Hole that proved the sinkhole had formed above sea level?
Stalactites
Stalactites form drip by drip in air-filled caves, so finding them underwater showed the hole stood dry before the seas rose. Some hang at a tilt, evidence that the land itself later shifted.
Q 03The Lusca, a monster of island folklore said to lurk in the blue holes of Andros, resembles which giant sea creature?
Octopus
Octopus tentacles are the Lusca's trademark: a guide on Andros called it Him of the Hands and told a visiting diver tales of it grabbing fishermen and sinking ships.
Q 04Legend says which figure from Journey to the West found his golden cudgel in Dragon Hole, a 300-metre-deep blue hole?
The Monkey King
The Monkey King's legend clings to a real place: Dragon Hole held the title of deepest known blue hole from 2016 until a rival was measured in 2024.
Q 05Sediment drilled from the Great Blue Hole strengthened the case that drought helped topple which ancient civilization?
Maya
Maya civilization collapsed between AD 800 and 1000, just when the hole's mud layers record far fewer storms. The sinkhole works like a giant bucket, trapping a record of past climate.
Q 06Which fruit names a deep blue hole off Sarasota, Florida, after a fishing captain saw its skin floating there?
Banana
Banana skin, a green one, gave Green Banana Hole its name. The sinkhole is shaped roughly like an hourglass, which makes it especially hard to explore.
Q 07The Blue Hole of Santa Rosa, a desert spring pool popular with scuba divers, sits beside which famous American highway?
Route 66
Route 66 brought motorists right past the pool from the 1920s, and its steady 62 °F water has since made it one of America's most popular spots for dive training.
Q 08Blue holes look deep blue because seawater absorbs the other colours of sunlight; which colour is absorbed first?
Red
Red light is soaked up first, then yellow and finally green, leaving blue to reach the white sand below and bounce back up.
Q 09Which British billionaire joined a submarine expedition to the bottom of the Great Blue Hole, broadcast live in 2018?
Richard Branson
Richard Branson rode along as two submarines scanned the walls with sonar, producing the first 3D map of the hole's interior.
Q 10The Great Blue Hole lies near the centre of which atoll, about 70 kilometres off the coast of Belize?
Lighthouse Reef
Lighthouse Reef is one of only three atolls in Belize, and at low tide parts of the coral ring around the hole break the surface.
Q 11What was the name of the research ship that carried a famous undersea explorer to chart the Great Blue Hole in 1971?
Calypso
Calypso was leased to her captain for a symbolic one franc a year, and John Denver's 1975 hit song of the same name was a tribute to the ship and her crew.
Q 12The Great Blue Hole belongs to a reef reserve system that earned which international designation in 1996?
World Heritage Site
World Heritage Site status covers seven protected areas along the reef, including the hole itself and the nearby island of Half Moon Caye.
Q 13Which television network ranked the Great Blue Hole first on its list of the ten most amazing places on Earth?
Discovery Channel
Q 21Local fishermen call Dragon Hole, a blue hole in the Paracel Islands, the eye of which body of water?
South China Sea
South China Sea coral around the hole lies under less than a metre of water, so researchers floated a flat-bottomed platform over it to lower their robot.
Q 22Dean's Blue Hole, a 202-metre-deep sinkhole in a bay near Clarence Town, is on Long Island in which island nation?
The Bahamas
The Bahamas is home to Dean's Blue Hole, whose mouth, about 30 metres wide, opens into a cavern more than three times that across.
Q 23Dean's Blue Hole hosts Vertical Blue, an invite-only elite competition in which sport?
Freediving
Discovery Channel came back in 2018 with a two-hour live special that followed submarines down to the floor of the sinkhole.
Q 14Which toxic gas forms a layer roughly 90 metres down in the Great Blue Hole, with dark, lifeless water beneath?
Hydrogen sulfide
Hydrogen sulfide marks the point where the sunlight vanishes: a submarine pilot who passed through the layer in 2018 described total blackness beneath it.
Q 15Which type of shark, a sedentary bottom-dweller, lives in the Great Blue Hole alongside blacktips and reef sharks?
Nurse
Nurse sharks often rest in groups by day and feed at night. The hole's coral rim starts about 5 metres down before dropping away as a near-vertical cliff.
Q 16The Great Blue Hole sits in the world's second-largest coral reef system; which country has the largest?
Australia
Australia's Great Barrier Reef is the only system bigger than the Mesoamerican reef, which runs along the coasts of four countries from the Yucatán Peninsula down to Honduras.
Q 17Which naturalist described Belize's barrier reef in 1842 as the most remarkable reef in the West Indies?
Charles Darwin
Charles Darwin published his theory of how coral atolls form that same year, drawing on his five-year voyage aboard HMS Beagle.
Q 18Which seabirds were the reason Half Moon Caye, near the Great Blue Hole, became a sanctuary in the 1920s?
Boobies
Boobies with brightly coloured feet nest in the island's rare orange-flowered forest, and their droppings fertilise the very trees that shelter them.
Q 19The Great Blue Hole sits inside an atoll, a ring of coral reef that encloses which kind of shallow water body?
Lagoon
Lagoon water around the hole is only 2 to 6 metres deep, which is why the dark shaft, more than 120 metres deep, stands out so sharply from the air.
Q 20Taam Ja', measured in 2024 as the deepest known blue hole, lies in Chetumal Bay off the coast of which country?
Mexico
Mexico's record-breaker was probed to more than 420 metres without the instruments finding the bottom, so its true depth is still unknown.
Freediving records fall here regularly: the first Vertical Blue, held over eleven days in 2008, produced 23 national and 3 world records.
Q 24William Trubridge, the first diver to pass 100 metres without fins, set records at Dean's Blue Hole for which country?
New Zealand
New Zealand became Trubridge's home at eighteen months old, after his birth in England, and he went on to run a diving school and an annual contest at the hole.
Q 25Which country is home to the Blue Hole of Dahab, a Sinai dive site nicknamed the Divers' Cemetery?
Egypt
Egypt's diving authority stationed a policeman at the site to check that divers go down with a certified guide, after a long run of fatal accidents.
Q 26Which tunnel in Dahab's Blue Hole, its roof 55 metres below the surface, has claimed the lives of many divers?
The Arch
The Arch looks under 10 metres long in the clear water but measures 26, and it lies well below the 40-metre limit usually set for recreational divers.
Q 27Which 2023 Netflix documentary about Italian record-chaser Alessia Zecchini features the deadly Blue Hole at Dahab?
The Deepest Breath
The Deepest Breath premiered at the Sundance Film Festival and follows Zecchini's pursuit of a world record with the help of safety diver Stephen Keenan.
Q 28Blue holes differ from which inland sinkholes, famous across the Yucatán and usually filled with fresh groundwater?
Cenotes
Cenotes are inland pits holding fresh groundwater, while blue holes typically hold seawater, or a mix, that rises and falls with the tide.
Q 29Blue holes develop in banks and islands of carbonate bedrock, most often which rock that rainwater slowly dissolves?
Limestone
Limestone exposed when sea levels stood more than 100 metres lower was eaten into caves and pits by rain, and the rising ocean later flooded them.
Q 30The deep water in most blue holes lacks which dissolved gas, making it hostile to fish but ideal for preserving fossils?
Oxygen
Oxygen runs out because the water barely circulates, and the same stillness lets mud settle in layers that record climate back to the last ice age.