Oceanography
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50 free Oceanography trivia questions with answers — science & nature quiz, new questions added Oct 2026.
Oceanography is the science of the sea itself: how the water moves, what is dissolved in it, what lies on the bottom and what manages to live there. It is a young science. Much of what it knows was learned in the last 150 years, often from ships lowering simple tools over the side. This quiz covers the basics a first course would teach. Expect questions on winds and moving water, the rise and fall of the sea along the shore, salt and chemistry, the landscape of the deep seabed, and the tiny drifting life that feeds everything else. There are also the people and expeditions behind the discoveries, and a few strange stories, including a spy mission and a shipment of lost bath toys. The questions suit students revising for a class, quiz bowl and Science Olympiad teams, and anyone who likes the sea. Each answer comes with a short explanation, so a wrong guess still teaches something.
30 of 50 questions with answers and explanations. Play the quiz
Q 01Which cargo, washed off a container ship in a 1992 storm, helped oceanographers trace surface currents for years?
Rubber ducks
Rubber ducks were among 28,800 bath toys lost overboard, and they kept washing up on distant beaches. Oceanographer Curtis Ebbesmeyer used beachcombers' finds to test a model of ocean currents.
Q 02Which seabed mineral lumps did the CIA pretend to be mining in 1974 while secretly raising a sunken Soviet submarine?
Manganese nodules
Manganese nodules were the cover story for Project Azorian, with Howard Hughes lending his name to the fake mining venture. The ship Hughes Glomar Explorer recovered a portion of the submarine K-129.
Q 03Which sea in the North Atlantic is the only one on Earth bounded by ocean currents instead of land?
Sargasso Sea
The Sargasso Sea is hemmed in by four currents and named after the brown Sargassum seaweed that floats on it in mats. European and American eels migrate there to spawn.
Q 04Which British warship's voyage of 1872 to 1876 is credited with laying the foundations of modern oceanography?
HMS Challenger
HMS Challenger sailed almost 69,000 nautical miles with laboratories on board, and its scientists found about 4,700 new species. A NASA space shuttle was later named after the ship.
Q 05Which warm Atlantic current did Benjamin Franklin chart in the 1700s to help mail ships cross faster from England?
Gulf Stream
The Gulf Stream was costing British mail packets weeks on the westbound crossing. Franklin had a sea captain named Folger sketch its path on a chart, with notes on how to steer clear of it.
Q 06Which naturalist proposed in 1842 that coral atolls form as reefs grow upward around slowly sinking volcanic islands?
Charles Darwin
Charles Darwin based the idea on reefs he had studied during the five-year voyage of HMS Beagle. He published it 17 years before On the Origin of Species.
Q 07Which crescent-shaped feature of the western Pacific seabed holds the deepest known point in any ocean?
Mariana Trench
The Mariana Trench drops nearly 11 kilometres. If Mount Everest stood on its floor, the summit would still lie more than 2 kilometres under water.
Q 08Which French naval officer co-invented the Aqua-Lung during World War II, freeing divers from surface air hoses?
Jacques Cousteau
Jacques Cousteau built it with engineer Émile Gagnan in occupied France over the winter of 1942 to 1943. He went on to use it to film beneath the waves.
Q 09Which microscopic drifting organisms produce about half of Earth's oxygen while making up only 1% of plant biomass?
Phytoplankton
Phytoplankton live in the sunlit surface layer, where they take in carbon dioxide and release oxygen. They also carry out about half of all the photosynthesis on Earth.
Q 10Which climate pattern starts when trade winds weaken and warm water surges east across the tropical Pacific?
El Niño
El Niño was named by Peruvian sailors after the Christ Child, because the warm water tended to show up around Christmas. Its cooler opposite phase is called La Niña.
Q 11Which result of Earth's rotation bends ocean currents right in the Northern Hemisphere and left in the Southern?
Coriolis effect
The Coriolis effect takes its name from French scientist Gaspard-Gustave de Coriolis, who set out the mathematics in an 1835 paper. His subject was water wheels, not the sea.
Q 12Which slow, density-driven flow of the deep ocean is nicknamed the global conveyor belt by climate scientists?
Thermohaline circulation
Thermohaline circulation is named from thermo for heat and haline for salt, the two things that set the density of seawater. Climate scientist Wallace Broecker coined the conveyor belt nickname.
Q 13Which name is given to the extra-large tidal ranges that occur at every new and full moon, in any season?
Q 21Which compound forms as seawater soaks up the main greenhouse gas from human emissions, lowering ocean pH?
Carbonic acid
Carbonic acid forms when carbon dioxide reacts with water, and the sea takes up roughly a quarter of what people emit. Corals and mollusks then find it harder to build shells and skeletons.
Q 22Which ocean layer, dividing the warm mixed surface water from the cold deep, can hide submarines by reflecting sonar?
Thermocline
The thermocline is where temperature falls fastest with depth, and the speed of sound falls with it. That bends or bounces sonar pings, so a submarine below the layer is harder to detect.
Q 23Which term names a vast rotating system of wind-driven surface currents, five of which dominate the subtropics?
Gyre
Spring tides
Spring tides are not named after the season. The word comes from an older sense of spring meaning to jump, burst forth or rise, as water does in a natural spring.
Q 14Which Canadian bay has the highest tidal range in the world, reaching about 16 metres thanks to its funnel shape?
Bay of Fundy
The Bay of Fundy rises and falls so far because the water resonates in its long, funnel-shaped basin. The typical range in the open ocean is only about one metre.
Q 15Which waves, usually set off by undersea earthquakes, cross deep ocean at jetliner speed yet pass ships unnoticed?
Tsunamis
Tsunamis travel at well over 800 km/h in deep water but stand only about a metre high there. Near the coast they slow below 80 km/h and the shallowing seabed squeezes them upward.
Q 16Which traditional unit of water depth equals six feet, originally the span of a man's outstretched arms?
Fathom
The fathom gets its name from an Old English word meaning embracing arms. Water past the 100-fathom line, too deep for a hand sounding line, was said to be off soundings.
Q 17Which American oceanographer led the 1985 expedition that found the wreck of the Titanic on the Atlantic seabed?
Robert Ballard
Robert Ballard was really at sea for the US Navy, which wanted secret surveys of two sunken nuclear submarines, Thresher and Scorpion. He was free to hunt for the liner with whatever time remained.
Q 18Which marine biologist wrote the 1951 bestseller The Sea Around Us, years before her famous warning about pesticides?
Rachel Carson
Rachel Carson won the 1952 National Book Award for Nonfiction with her history of the oceans. It stayed on the New York Times Best Seller List for 86 weeks.
Q 19Which discarded items make up nearly half the mass of the Great Pacific Garbage Patch, according to a 2018 study?
Fishing nets
Fishing nets, lost or dumped at sea, dominate the debris by weight. Sailor Charles Moore drew the world's attention to the floating rubbish after crossing it on his way home from a 1997 yacht race.
Q 20Roughly what share of seawater's weight is dissolved salts, which come mainly from rocks on land and seabed openings?
About 3.5%
About 3.5% is the ocean average, which oceanographers usually write as a salinity of 35 parts per thousand. Rain slowly erodes rocks, and rivers carry the freed ions down to the sea.
A gyre turns clockwise north of the equator and counterclockwise south of it in the subtropics. Floating plastic gathers inside these loops, which is how the ocean's rubbish patches form.
Q 24Which process off Peru and California lets just 5% of the ocean yield about a quarter of the world's fish catch?
Upwelling
Upwelling is the wind-driven rise of cold, dense water from the deep to replace surface water pushed offshore. The nutrients it carries fertilise the algae that feed huge shoals of fish.
Q 25Which gently sloping, shallow seabed bordering most coastlines was largely dry land during the ice ages?
Continental shelf
The continental shelf ends at a drop-off that lies about 140 metres down almost everywhere. That uniform depth is thought to mark where the shoreline stood when ice sheets locked up the water.
Q 26Which process, proposed by Harry Hess and Robert Dietz in the 1960s, forms new ocean crust at mid-ocean ridges?
Seafloor spreading
Seafloor spreading grew out of Hess's wartime service. As captain of a US Navy transport he kept the ship's echo sounder running across the Pacific and charted the seabed as he went.
Q 27Which American geologist mapped the Atlantic floor in the 1950s and found the rift valley along its central ridge?
Marie Tharp
Marie Tharp drew her maps on land from depth soundings that Bruce Heezen gathered aboard ship. Women were barred from working on research vessels for the first 18 years of their partnership.
Q 28Near which Pacific archipelago did scientists diving in Alvin find the first hydrothermal vents in 1977?
Galápagos Islands
The Galápagos Islands lie beside a rift where geologists expected to find warm water. They were astounded to find the vents teeming with life, including clams and giant tube worms.
Q 29Which process lets bacteria at deep-sea hydrothermal vents make food from hydrogen sulfide without any sunlight?
Chemosynthesis
Chemosynthesis feeds whole communities in the dark. Giant tube worms house the bacteria inside their bodies and live on the sugars the microbes make.
Q 30Which bathyscaphe carried Jacques Piccard and Don Walsh to the deepest known point in the ocean in 1960?
Trieste
Trieste took 4 hours 47 minutes to sink to the bottom, and an outer window pane cracked on the way down. The two men stayed just twenty minutes before starting back up.