The L Boat is a type of sail sloop racing boat designed by the Luedtke Brothers in Toledo, Ohio in May, 1931. The boats were of wood construction with low freeboard. Most of the hulls were mahogany, but a few were redwood and cedar. They were 28 feet (8.5 m) long, 7¹/₂ foot beam, and 3¹/₂ foot draft. They also had an iron centerboard that could be lowered to increase the draft to six feet and assist in upwind sailing. They had a very large mainsail with relatively small headsails and a 3/4s rig. The 40-foot (12 m) tall mast was sitka spruce with stainless rigging.

The first 40 were built by Luedtke; Remi DeBlaere built the last 11. The last hulls were #50 and #51. They were raced One-Design in Detroit from the 1930s thru the 1960s until the class fell apart in 1968 due to the rise of fiberglass in ship construction. The Sally K (Hull #30) is the last remaining L Boat in Detroit. Her hull is redwood. She is docked at the Windmill Pointe Park marina where the Detroit River meets Lake St. Clair.

A boat is a watercraft of any size designed to float or plane, to provide passage across water. Usually this water will be inland (lakes) or in protected coastal areas. However, boats such as the whaleboat were designed to be operated from a ship in an offshore environment. In naval terms, a boat is a vessel small enough to be carried aboard another vessel (a ship). Another less restrictive definition is a vessel that can be lifted out of the water. Strictly speaking and uniquely a submarine is a boat as defined by the Royal Navy^{[citation needed]}. Some boats too large for the naval definition include the Great Lakes freighter, riverboat, narrowboat and ferryboat. The term armed boat, used primarily by English speaking naval forces, referred to any boat carrying either a cannon or armed occupants, such as marines^{[citation needed]}.

Boats have served as short-distance transportation since early times. Circumstantial evidence, such as the early settlement of Australia over 40,000 years ago, and findings in Crete dated 130,000 years ago, suggests that boats have been used since ancient times. The earliest boats have been predicted to be logboats. The oldest boats to be found by archaeological excavation are logboats from around 7,000–10,000 years ago. The oldest recovered boat in the world is the Pesse canoe; it is a dugout or hollowed tree trunk from a Pinus sylvestris. It was constructed somewhere between 8200 and 7600 B.C. This canoe is exhibited in the Drents Museum in Assen, Netherlands; other very old dugout boats have been recovered. A 7,000 year-old seagoing boat made from reeds and tar has been found in Kuwait.