A boat was a watercraft of any size designed to float or plane, to provide passage across water.
History
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 reason for the crew's disappearance remained a mystery. (DW: The Chase) At some point the crew of the Mary Celeste were abducted by Arcturans. (DWAN: The Mystery of the Marie Celeste)
Ben Jackson was assigned to the Royal Navy ship, HMS Teazer. (DW: The War Machines)
HMS Victory was the flagship of Lord Admiral Horatio Nelson during the Battle of Trafalgar. (DWAN: 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. (DW: Carnival of Monsters)
As well as hovercraft, the workers at the Delta III refinery used rowing boats to traverse the swamps, as did the native Swampies. (DW: 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. (DW: The Invasion of Time)
The Eternals used replicas of boats from various periods of Earth history (literally, space ships) while conducting a race in space to reach Enlightenment. (DW: 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. (BFA: The Sirens of Time)
Captain Callany owned a steamboat called the Lankester that sailed from Madagascar to New Orleans every year. First mate 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. (BFA: 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. (DWM: 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. (DW: The Curse of the Black Spot)