Some vessels carry boats so there is no lower limit.
Ships, boats etc used for military purposes.
100ft.
Submarines are commonly referred to as "boats" due to naval tradition, which dates back to the early days of maritime language. Historically, smaller vessels were called boats, while larger ships were referred to as ships. This terminology has persisted, and even though submarines are technically large underwater vessels, they retain the "boat" designation as a nod to their origins and the conventions of naval terminology.
100ft
Personal Watercraft (PWC) Fishing boats Recreational powerboats Military or naval craft
Traditionally it was vessels under 200 feet long. Vietnam Riverine Boats (Brown Water Navy) were all considered boats; Swift Boats (PCF-Patrol Craft Fast), PBR's (Patrol Boat River), Monitors (River Battleships), and Alpha Boats (ASPB-Assault Support Patrol Boats). Blue Water Naval vessels were Frigates, Destroyers, Cruisers, etc.
Boats must give way to other boats that are less maneuverable, such as larger vessels, vessels not under command, vessels restricted in their ability to maneuver, and vessels engaged in fishing.
U-boats were for attacking enemy shipping.
During World War I and II, Germany utilized various vessels in the Atlantic, including U-boats (submarines), surface raiders, and battleships. U-boats were particularly significant for disrupting Allied shipping through unrestricted submarine warfare. Notably, in World War II, vessels like the battleship Bismarck and the pocket battleship Admiral Graf Spee engaged in commerce raiding and naval battles in the Atlantic. These naval operations aimed to weaken Allied supply lines and assert Germany's naval power.
Excursion Boats Naval Parade - 1898 was released on: USA: September 1898
Police Boats Escorting Naval Parade - 1898 was released on: USA: September 1898
Blood vessels