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50 free Great Barrier Reef trivia questions with answers — geography quiz, new questions added Aug 2026.
The Great Barrier Reef is the largest thing on Earth built by living creatures, a chain of 2,900 reefs and 900 islands running 2,300 km down the coast of Queensland that astronauts can pick out from orbit. This quiz starts with the numbers a beginner can enjoy (how long, how many reefs, which sea, which state) and works up to the geology: why Queensland was too cold for coral until 24 million years ago, why the living reef is only 6,000 to 9,000 years old, and what a 'wonky hole' is. It then meets the wildlife: 1,500 fish species, six kinds of sea turtle, dugongs grazing 15 species of seagrass, 30 kinds of whale and dolphin, mass coral spawning after the October full moon, and the crown-of-thorns starfish that eats it all. History gets its share with Cook's grounding in 1770, Matthew Flinders' naming, the wreck of HMS Pandora and 40,000 years of Aboriginal use, before the quiz turns to bleaching, farm runoff, shipping accidents, shark culling, the Reef 2050 plan and the reef's premature obituary in 2016. Every answer was checked against Wikipedia's articles on the Great Barrier Reef and its wildlife, and each question shows the sentence that supports it. Try our Australia, coral reefs and ocean quizzes next.
30 of 50 questions with answers and explanations. Play the quiz
Q 01The Great Barrier Reef lies off the coast of which Australian state?
Queensland
It sits in the Coral Sea, separated from the mainland by a channel up to 160 km wide.
Q 02Roughly how many individual reefs make up the Great Barrier Reef?
Over 2,900
It also includes about 900 islands and stretches more than 2,300 km.
Q 03The reef is described as the world's biggest single structure made by what?
Living organisms
It was built by billions of tiny coral polyps and can be seen from outer space.
Q 04In which year was the Great Barrier Reef selected as a World Heritage Site?
1981
CNN named it one of the Seven Natural Wonders of the World in 1997.
Q 05Which explorer was the first European to encounter the Great Barrier Reef, in 1770?
James Cook
His ship Endeavour ran aground on 11 June 1770 near today's Cooktown and took seven weeks to repair.
Q 06Who gave the Great Barrier Reef its name after mapping it in detail in 1802?
Matthew Flinders
He used 'barrier reef' for any reef that kept ocean swell or ships from reaching the coast.
Q 07Cook's ship that struck the reef in 1770 was named what?
Endeavour
The crew lightened the ship and refloated it on the incoming tide.
Q 08Which famous ship sank on the reef on 29 August 1791, killing 35 men?
HMS Pandora
The Queensland Museum has excavated the wreck since 1983; over 1,600 wrecks are known in the reef region.
Q 09Aboriginal Australians have lived in the reef region for at least how long?
40,000 years
Torres Strait Islanders arrived about 10,000 years ago; some 70 clan groups hold the reef as a cultural feature.
Q 10The reef's northernmost island, in the Torres Strait, is called what?
Bramble Cay
Lady Elliot Island, 1,915 km to the south-east, marks the other end.
Q 11Until about 25 million years ago, why could coral not grow off north-eastern Australia?
The water was too cool
Australia has been drifting north about 7 cm a year, and Queensland only entered tropical waters around 24 million years ago.
Q 12The current living reef structure is believed to have begun growing roughly how long ago?
9,000 years
It sits on much older limestone platforms; the sea level at that time was about 120 metres lower than today.
Q 13Coral reefs need sunlight, so the reef cannot grow below what depth?
150 metres
Reefs also cannot grow above sea level; they gain 1 to 25 cm in height a year.
Q 21Reefs of the inner Great Barrier Reef mass-spawn during the week after the full moon in which month?
October
Outer reefs follow in November and December; the event is cued by rising water temperature and the lunar cycle.
Q 22How many coral species, hard and soft, inhabit the reef?
About 400
Fast-growing Acropora is the dominant type and drove the record recovery reported in 2022.
Q 23How many species of sea snake live on the reef?
Seventeen
None is endemic or endangered, and they are more common in the southern section.
Q 24Close to how many mollusc species have been recorded on the reef?
Q 14Which reef feature, found in the northern Great Barrier Reef, is not found anywhere else in the system?
Ribbon reefs
The system has no atolls at all, and reefs attached to the mainland are rare.
Q 15A previously undiscovered reef found in the northern area in 2020 stands how tall?
500 metres
It is 1.5 km wide at its base, taller than the Empire State Building.
Q 16What is a 'wonky hole'?
A freshwater upwelling
The nutrient-rich freshwater can cause local eutrophication.
Q 17Roughly how many species of fish live on the Great Barrier Reef?
Over 1,500
They include the clownfish, red bass, red-throat emperor, snappers and coral trout.
Q 18How many species of sea turtle come to the reef to breed?
Six
Green, leatherback, hawksbill, loggerhead, flatback and olive ridley all nest there.
Q 19Which large seagrass-grazing marine mammals live in big populations on the reef?
Dugongs
Fifteen species of seagrass feed them and the turtles; native title holders may still hunt them for personal use.
Q 20How many species of cetacean have been recorded on the Great Barrier Reef?
Thirty
They include the dwarf minke whale, Indo-Pacific humpback dolphin and humpback whale.
5,000
They include the giant clam, nudibranchs and cone snails.
Q 25Between 1.4 and 1.7 million of what use the reef's islands to breed?
Birds
215 bird species visit, nest or roost, including the white-bellied sea eagle and roseate tern.
Q 26Which starfish preys on coral polyps and periodically devastates the reef?
Crown-of-thorns
A 2000 outbreak stripped 66% of live coral on sampled reefs; the animal has up to 21 venomous arms.
Q 27Fertiliser runoff helps the coral-eating starfish because a doubling of chlorophyll does what to larval survival?
Increases it tenfold
More phytoplankton means more food for the larvae, which is why farm runoff feeds outbreaks.
Q 28What does the Great Barrier Reef Marine Park Authority consider the single greatest threat to the reef?
Climate change
Warmer seas drive coral bleaching, which struck in 1998, 2002, 2006, 2016, 2017 and 2020.
Q 29Coral bleaching happens when stressed corals lose what?
Their symbiotic algae
The zooxanthellae give coral its colour and feed it through photosynthesis; without them the coral starves.
Q 30A 2020 study found the reef had lost what share of its coral cover since 1995?
More than half
A 2012 study had already reported the same for the period since 1985.