A boat was a watercraft of any size designed to float or plane, to provide passage across water.
The First Doctor landed his TARDIS aboard the Mary Celeste. They were followed by a group of Daleks, who scared the crew so much that they jumped overboard. This was not witnessed by anyone else, so the crew's disappearance remained a mystery. (TV: The Chase) The crew of the Mary Celeste were abducted by Arcturans. (PROSE: The Mystery of the Marie Celeste)
Ben Jackson was assigned to the Royal Navy ship, HMS Teazer. (TV: The War Machines)
HMS Victory was the flagship of Lord Admiral Horatio Nelson during the Battle of Trafalgar. (PROSE: H.M.S. TARDIS)
The SS Bernice was a cargo ship. It was sailing from Bombay when the crew were taken into a miniscope where they boarded a replica of the ship. With the aid of the Third Doctor, they eventually returned to the real ship. (TV: Carnival of Monsters)
in 1889, George Litefoot was able to acquisition a rowing boat so the Fourth Doctor and he could find the confluence of the River Thames and River Fleet. (TV: The Talons of Weng-Chiang)
As well as hovercraft, the workers at the Delta III refinery used rowing boats to traverse the swamps, as did the native Swampies. (TV: The Power of Kroll)
RMS Titanic was a luxury ocean liner that sank on its maiden voyage in 1912. The Fourth Doctor owned a copy of the Daily Mirror detailing this event. (TV: The Invasion of Time)
The Eternals used replicas of boats from many periods of Earth history (literally, space ships) while conducting a race in space to reach Enlightenment. (TV: Enlightenment)
RMS Lusitania was an ocean liner sunk by the U-20 during World War I. This act finally convinced the United States of America to join the war. (AUDIO: The Sirens of Time)
Captain Callany owned a steamboat called the Lankester that sailed from Madagascar to New Orleans every year. First mate Jacques de Requin brought a mermaid. The Lankester sank after it ran aground on some rocks. The Sixth Doctor convinced the mermen to save the crew. (AUDIO: Cryptobiosis)
The Sixth Doctor and Frobisher used a steamboat called the Sea Sharp to travel to and from Professor Strut's island on the planet Zazz. (COMIC: The Gift)
The Fancy was the ship of Henry Avery. Many of its crew were taken by a virtual doctor who deemed them to be ill. The Eleventh Doctor, Amy Pond, and Rory Williams boarded the Fancy through the The Doctor's TARDIS once the TARDIS sensors responded to a ship in distress. (TV: The Curse of the Black Spot)
On Earth, some individuals lived aboard houseboats. In the mid-1990s, Kate Lethbridge-Stewart lived with her son Gordy in such a boat on a river. (HOMEVID: Downtime)