Swamp

A swamp or marsh was an area of land partially covered with shallow water. The Doctor encountered swamps on many planets in his travels, including one inside Vorg's miniscope (TV: Carnival of Monsters) and one in the Matrix. (TV: The Deadly Assassin)

Swamps on Earth
The Ninth Doctor said that London used to be marshland. (TV: World War Three) The Eleventh Doctor said likewise about Venice. (TV: The Vampires of Venice)

Redvers Fenn-Cooper once visited a swamp full of giant lizards like giant dinosaurs. (TV: Ghost Light)

The Eleventh Doctor, Amy Pond and Rory Williams visited a swamp in 1929 Louisiana. (COMIC: Terror from the Swamp) The Sixth Doctor and Melanie Bush visited a Louisiana swamp in 1957. (PROSE: Swamp of Horrors (1957) - Viewing Notes) The Eighth Doctor visited a Louisiana swamp in the early 21st century. (PROSE: The City of the Dead)

Swamps on other planets
Planets which had swamps included Alzarius, (TV: Full Circle) Corbo, (PROSE: The Devil-Birds of Corbo) Delta III, (TV: The Power of Kroll) Desperus, (TV: The Daleks' Master Plan) Diamedes, (PROSE: Detour to Diamedes) Gameworld Gamma, (COMIC: The Hunt of Doom) Gurnian, (COMIC: Monsters of Gurnian) the Haunted Planet, (COMIC: The Haunted Planet) Ogros, (TV: The Stones of Blood) Sunday, (PROSE: Wetworld) Terroth (COMIC: Planet of Serpents) and Zom. (COMIC: City of the Damned)

The Second Doctor, John and Gillian visited a swamp planet inhabited by giant spiders controlled by the Master of Spiders. (COMIC: Master of Spiders) They also visited a different swamp planet where they battled witches. (COMIC: Return of the Witches)

A swamp planet in the Calysteral cluster was used by the Judoon as a prison. (TV: The Vault of Secrets)

Sancroff was imprisoned on a swamp planet. (AUDIO: The Sirens of Time)

The Tenth Doctor and Donna Noble visited a planet where an entire swamp was a single organism. (COMIC: The Time of My Life)