This guide collects ocean answers from the “Ocean Facts” pages of the US National Oceanic and Atmospheric Administration (NOAA), for use in writing quiz questions. Each page quoted here shows “Last updated: 09/23/26” (US date format) except the Atlantic page, which shows 1/04/21. The figures below are NOAA’s own, in the units it gives.
Trap one: how many oceans are there?
NOAA’s answer starts with “There is only one global ocean.” It explains that this water, covering 71 percent of the Earth, is geographically divided into named regions. Historically there are four named oceans: the Atlantic, Pacific, Indian and Arctic. NOAA says most countries, including the United States, now recognise the Southern (Antarctic) as the fifth.
The Southern Ocean is described as the newest. The US Board on Geographic Names recognises it as the water from the coast of Antarctica to 60 degrees South. NOAA says its boundaries were proposed to the International Hydrographic Organization in 2000, but not all countries agree on them, so the proposal has yet to be ratified by members of that body.
Trap two: oceans, seas and the “Seven Seas”
In geography, NOAA says, seas are smaller than oceans and usually located where land and ocean meet, typically partially enclosed by land. The Sargasso Sea is the exception it names, because it is defined only by ocean currents.
The “Seven Seas” have no single list. NOAA says the exact origin of the phrase is uncertain. In Greek literature the seven were the Aegean, Adriatic, Mediterranean, Black, Red and Caspian seas, with the Persian Gulf thrown in. Medieval European writing used the North Sea, Baltic, Atlantic, Mediterranean, Black, Red and Arabian seas. NOAA says the modern Seven Seas could be given as the Arctic, North Atlantic, South Atlantic, North Pacific, South Pacific, Indian and Southern oceans, though the ocean is more commonly divided into five.
Biggest, second biggest, smallest
NOAA says the Pacific is the largest and deepest of the world ocean basins, containing more than half of the free water on Earth. Its order is Pacific, then Atlantic, then Indian, then Southern, and finally the Arctic. Two NOAA pages give the Pacific’s area differently: one says approximately 63 million square miles, another approximately 155 million square kilometres (59 million square miles). A question asking for an exact area therefore needs to say which source it follows.
On the Atlantic, NOAA gives approximately 106,460,000 square kilometres (41,105,000 square miles), about 20 percent of the Earth’s surface, and calls it only slightly larger than half the size of the Pacific. The Arctic is the smallest at about 6.1 million square miles, which NOAA says is about 1.5 times as big as the United States.
The Pacific’s name has a date attached. NOAA says Ferdinand Magellan, whose fleet entered the ocean in November 1520, called it “pacific” because of the calmness of the water at the time. The Atlantic, it adds, takes its name from the Greek god Atlas.
Depth, water and salt
NOAA gives the average ocean depth as about 3,682 metres (12,080 feet). The deepest part is the Challenger Deep, at the southern end of the Mariana Trench beneath the western Pacific, approximately 10,935 metres (35,876 feet) deep. It is named after HMS Challenger, whose crew first sounded the depths of the trench in 1875.
On volume, NOAA says about 97 percent of Earth’s water is in the ocean, and less than one percent of all water on Earth is fresh. Ocean salt, it says, comes primarily from rocks on land and openings in the seafloor. Average salinity is about 35 parts per thousand, or about 3.5 percent of the weight of seawater, and chloride and sodium make up around 85 percent of the dissolved ions.
Tides and a hidden waterfall
NOAA says the highest tides in the world are in Canada, in the Bay of Fundy, at Burntcoat Head in Nova Scotia. It also calls it a misconception that the range of the tide increases with latitude, and says that idea is incorrect. It says the higher ranges seen in Alaska, Canada and northern Europe are created by the positions and configurations of the continents in the northern hemisphere.
The world’s largest waterfall, NOAA says, is in the ocean beneath the Denmark Strait, which separates Iceland and Greenland. Its cataracts begin 2,000 feet under the surface of the strait and plunge to a depth of 10,000 feet at the southern tip of Greenland, nearly a two-mile drop.
Quick answers for the quiz bag
- Oceans: one global ocean with named regions, four historically and five as now recognised by most countries including the United States.
- Largest: the Pacific. Smallest: the Arctic.
- Deepest point: Challenger Deep, about 10,935 metres.
- Highest tides: the Bay of Fundy, Canada.
- Largest waterfall: beneath the Denmark Strait.
The bottom line
NOAA’s pages let a quiz writer take ocean answers from one issuing body, and they show where an answer depends on definition or source: the number of oceans, the list of Seven Seas, and the Pacific’s area, which two NOAA pages give differently. The largest ocean, the Challenger Deep and the Bay of Fundy each have one answer stated on a NOAA page.
Sources
- How many oceans are there?, NOAA National Ocean Service, last updated 09/23/26, read 2 November 2026 (oceanservice.noaa.gov)
- What’s the difference between an ocean and a sea?, NOAA National Ocean Service, last updated 09/23/26, read 2 November 2026 (oceanservice.noaa.gov)
- What are the Seven Seas?, NOAA National Ocean Service, last updated 09/23/26, read 2 November 2026 (oceanservice.noaa.gov)
- What is the largest ocean basin on Earth? and What is the world’s smallest ocean?, NOAA National Ocean Service, last updated 09/23/26, read 2 November 2026 (oceanservice.noaa.gov)
- How did the Pacific Ocean get its name?, NOAA National Ocean Service, last updated 09/23/26, read 2 November 2026 (oceanservice.noaa.gov)
- How big is the Atlantic Ocean?, NOAA National Ocean Service, last updated 1/04/21 as shown, read 2 November 2026 (oceanservice.noaa.gov)
- How deep is the ocean?, How much water is in the ocean? and Why is the ocean salty?, NOAA National Ocean Service, last updated 09/23/26, read 2 November 2026 (oceanservice.noaa.gov)
- Where is the highest tide? and Where is Earth’s largest waterfall?, NOAA National Ocean Service, last updated 09/23/26, read 2 November 2026 (oceanservice.noaa.gov)
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