Sea

A sea was a large body of liquid.

Quinnis had a purple sea (COMIC: A Religious Experience)

According to Greek mythology, Poseidon was the god of the sea and the earthquakes. (TV: Planet of Fire)

Thoros-Beta had a number of seas, including the Sea of Despair and Longing, the Sea of Sorrows and the Sea of Turmoil. (TV: Mindwarp)

Sskendass-giis was a dried up sea bed on the planet Mars, known in English as the Dead Ocean of the Forsaken. (PROSE: GodEngine)

Samantha Jones felt "the first twinges" of agoraphobia when she was on Hyspero, a planet with deserts and seas that seemed to go on forever. (PROSE: The Scarlet Empress)

The Barian Sea on Moldox had golden water, and the beaches formed from grains of ice. (PROSE: Engines of War)

In 2006, the Slitheen family hid their spaceship in the North Sea and sent it to London as part of their plan to destroy Earth. (TV: Aliens of London / World War Three)

The TARDIS materialised on a schooner in the Caribbean Sea in 1800. When the Tenth Doctor and Martha Jones went out to explore, they were apprehended by the crew and nearly thrown overboard. (COMIC: Second Wave)

In 39 BC, the Eleventh Doctor, Amy Pond and Rory Williams arrived on a Roman ship in the Mediterranean Sea which was unknowingly transporting a Gold Assassin to Cleopatra. (COMIC: Golden Slumbers)

There were several areas on the Moon called seas, including the Sea of Crises, the Sea of Ingenuity, the Sea of Nectar, and the Sea of Tranquility. (TV: Kill the Moon)

The seas of Marinus (TV: "The Sea of Death"), 16 Alpha Leonis One (PROSE: Eternity Weeps) and Endpoint were all composed of acid. (PROSE: Hope)

The Silvasic Sea was the largest body of water on Dellah. (PROSE: Dry Pilgrimage)

Alternative timeline
In an alternative timeline during The Year That Never Was, poisoned the Caspian Sea. (TV: Last of the Time Lords) Martha Jones later visited it during her travels around the globe. (PROSE: The Story of Martha)