A boat is a watercraft of a large range of types and sizes, but generally smaller than a ship, which is distinguished by its larger size or capacity, its shape, or its ability to carry boats.
A multihull is a boat or ship with more than one hull, whereas a vessel with a single hull is a monohull. The most common multihulls are catamarans, and trimarans. There are other types, with four or more hulls, but such examples are very rare and tend to be specialised for particular functions.
A catamaran is a watercraft with two parallel hulls of equal size. The distance between a catamaran's hulls imparts resistance to rolling and overturning. Catamarans typically have less hull volume, smaller displacement, and shallower draft (draught) than monohulls of comparable length. The two hulls combined also often have a smaller hydrodynamic resistance than comparable monohulls, requiring less propulsive power from either sails or motors. The catamaran's wider stance on the water can reduce both heeling and wave-induced motion, as compared with a monohull, and can give reduced wakes.
A seaplane is a powered fixed-wing aircraft capable of taking off and landing (alighting) on water. Seaplanes are usually divided into two categories based on their technological characteristics: floatplanes and flying boats; the latter are generally far larger and can carry far more. Seaplanes that can also take off and land on airfields are in a subclass called amphibious aircraft, or amphibians. Seaplanes were sometimes called hydroplanes, but currently this term applies instead to motor-powered watercraft that use the technique of hydrodynamic lift to skim the surface of water when running at speed.
An amphibious aircraft, or amphibian, is an aircraft that can take off and land on both solid ground and water. These aircraft are typically fixed-wing, though amphibious helicopters do exist as well. Fixed-wing amphibious aircraft are seaplanes which are equipped with retractable wheels, at the expense of extra weight and complexity, plus diminished range and fuel economy compared with planes designed specifically for land-only or water-only operation. Some amphibians are fitted with reinforced keels which act as skis, allowing them to land on snow or ice with their wheels up.
A pontoon bridge, also known as a floating bridge, uses floats or shallow-draft boats to support a continuous deck for pedestrian and vehicle travel. The buoyancy of the supports limits the maximum load that they can carry.
A trimaran is a multihull boat that comprises a main hull and two smaller outrigger hulls which are attached to the main hull with lateral beams. Most modern trimarans are sailing yachts designed for recreation or racing; others are ferries or warships. They originated from the traditional double-outrigger hulls of the Austronesian cultures of Maritime Southeast Asia; particularly in the Philippines and Eastern Indonesia, where it remains the dominant hull design of traditional fishing boats. Double-outriggers are derived from the older catamaran and single-outrigger boat designs.
A floating dock, floating pier or floating jetty is a platform or ramp supported by pontoons. It is usually joined to the shore with a gangway. The pier is usually held in place by vertical poles referred to as pilings, which are embedded in the seafloor or by anchored cables. Frequently used in marinas, this type of pier maintains a fixed vertical relationship to watercraft secured to it, independent of tidal, river or lake elevation. The angle of the gangway varies with the water level.
A floatplane is a type of seaplane with one or more slender floats mounted under the fuselage to provide buoyancy. By contrast, a flying boat uses its fuselage for buoyancy. Either type of seaplane may also have landing gear suitable for land, making the vehicle an amphibious aircraft. British usage is to call floatplanes "seaplanes" rather than use the term "seaplane" to refer to both floatplanes and flying boats.
Neutral buoyancy occurs when an object's average density is equal to the density of the fluid in which it is immersed, resulting in the buoyant force balancing the force of gravity that would otherwise cause the object to sink or rise. An object that has neutral buoyancy will neither sink nor rise.
Very large floating structures (VLFSs) or very large floating platforms (VLFPs) are artificial islands, which may be constructed to create floating airports, bridges, breakwaters, piers and docks, storage facilities, wind and solar power plants, for military purposes, to create industrial space, emergency bases, entertainment facilities, recreation parks, mobile offshore structures and even for habitation. Currently, several different concepts have been proposed for building floating cities or huge living complexes. Some units have been constructed and are presently in operation.
A pontoon boat is a flattish boat that relies on floats to remain buoyant. These pontoons contain much reserve buoyancy and allow designers to create large deck plans fitted with a variety of accommodations including expansive lounge areas, stand-up bars, and sun pads. More horsepower is now able to be applied to the stern due to design improvements. Pontoon boat drafts may be as shallow as eight inches, which reduces risk of running aground and underwater damage; this allows it to come close to shore to pick up and drop off loads.
The Navy Lighterage pontoon (NLP) was a type of pontoon developed in World War II by Capt. John N. Laycock Civil Engineer Corps (CEC) and used by United States Navy Construction Battalions (Seabees) on invasion beaches and shallow harbors or harbors where the facilities had been destroyed or did not exist. It was referred to as the Seabee's "magic box". It was Lego-like system of pre-cut pre-drilled angle iron and steel plate. It was first assembled into individual boxes that were joined in multiples to construct docks, causeways, barges, dry docks, floating cranes, marine railways or whatever was needed.
A rhino ferry is a barge constructed from several pontoons which are connected and equipped with outboard engines, used to transport heavy equipment and people. Rhino ferries were used extensively during the Normandy landings and other theaters ; their low draft was well-suited for shallow beaches, and they could also be used as piers when filled with water. An alternative to tank landing craft, they were operated by United States Navy Construction Battalions. They ferried their cargo from the outlying Landing Ships, Tank to the shore.
Naval Advance Base Espiritu Santo or Naval Base Espiritu Santo, most often just called Espiritu Santo, was a major advance Naval base that the U.S. Navy Seabees built during World War II to support the Allied effort in the Pacific. The base was located on the island of Espiritu Santo in the New Hebrides, now Vanuatu, in the South Pacific. The base also supported the U.S. Army and Army Air Corps, U.S. Coast Guard, and US Marine Corps. It was the first large advance base built in the Pacific. By the end of the war it had become the second-largest base in the theater. To keep ships tactically available there was a demand for bases that could repair and resupply the fleet at advance locations, rather than return them to the United States. Prior to December 7th, Pearl Harbor was the U.S. fleet's largest advance base in the Pacific. Espiritu became capable of all aspects necessary to support the Fleet's operations from fleet logistics in fuel, food, and ammunition, to transport embarkation for combat operations or returning to the continental United States. The ship repair facilities and drydocks were capable of attending to most damage and routine maintenance. Had it not existed, ships would have had to return to Pearl Harbor, Brisbane, or Sydney for major repairs and resupply. The base became a major R and R destination for the fleet.
Naval Base Banika Island was a United States Navy base built during World War II on Mbanika Island in the Russell Islands, part of the Solomon Islands. A larger supply depot was built to support the ships fighting in the Pacific War. Also built were a repair base for landing craft, PT boats, and other boats. Banika Island offered excellent fleet anchorage. Banika Island was taken during the Solomon Islands campaign. Also at the base was built the Renard Sound Seaplane Base.
