Float (nautical)

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The British racing seaplane Supermarine S.6B (1931) Supermarine S.6B ExCC.jpg
The British racing seaplane Supermarine S.6B (1931)

Floats (also called pontoons) are airtight hollow structures, similar to pressure vessels, designed to provide buoyancy in water. Their principal applications are in watercraft hulls, aircraft floats, floating pier, pontoon rhinos, pontoon causeways, and marine engineering applications such as salvage.


During WWII the United States Navy Civil Engineer Corps developed a modular steel box (pontoon) for the Seabees to use. It was an industrial sized Lego system of pre-drilled pre-cut angle iron and steel plate that could be assembled anywhere for which they became famous. They used them to facilitate amphibious landings. With the pontoons Seabees assembled docks, causeways, and rhinos to whatever size needed. They allowed landings on Sicily where no-one thought possible. They ferried Patton across the Rhine and put the Marines ashore on Okinawa. They would be used post-war at Inchon in 1950 and again in Lebanon in 1958.

Various objects that make use of floats are often referred to synecdochically as pontoons.


Floats make up the multipart hulls of catamarans and trimarans and provide buoyancy for floatplanes, seaplanes and houseboats. [1] They are used in pontoon bridges, floating piers, and floats anchored to the seabed for recreation or dockage. They are also used in shipbuilding and marine salvage, often deployed uninflated then pressurized to raise a sunken object. In military, floats are used as pontoon bridges or transportation platforms for heavier vehicles or machinery.

In popular usage, the term pontoon can refer to any of several of the following objects that make use of nautical floats.

Pontoon boat

A pontoon boat is a flattish boat that relies on nautical floats for buoyancy. Common boat designs are a catamaran with two pontoons, or a trimaran with three. [2] In many parts of the world, pontoon boats are used as small vehicle ferries to cross rivers and lakes. [3]

An anchored raft-like platform used for diving, often referred to as a pontoon Photo of pontoon (buoyant platform) taken at Port Vincent, South Australia.jpg
An anchored raft-like platform used for diving, often referred to as a pontoon

Anchored recreational platform

Raft-like platforms used for diving and other recreational activities are sometimes anchored at beaches and lake shores, often seasonally. Such platforms may be supported by foam-filled plastic floats or air-filled pontoons, and are known simply as "pontoons" in Australia and New Zealand. [4] [ better source needed ] They may also be called swim floats.[ citation needed ]

Floating dock

A floating dock, floating pier or floating jetty consists of a platform or ramp supported by nautical floats. It is sometimes joined to the shore with a gangway but can be laid out the whole way from the shore to the end. This type of pier maintains a fixed vertical relationship to watercraft secured to it.

Pontoon bridge

A pontoon bridge (also known as a ponton bridge or floating bridge) uses floats or shallow-draft boats to support a continuous deck for pedestrian and vehicle travel. Most, but not all, pontoon bridges are temporary, used in wartime and civil emergencies. [5] Seattle in the US and Kelowna in British Columbia, Canada are two places with permanent pontoon bridges, see William R. Bennett Bridge in British Columbia and these in Seattle: Lacey V. Murrow Memorial Bridge, Evergreen Point Floating Bridge and Homer M. Hadley Memorial Bridge.

Floats on a Cessna 208 Caravan 1 floatplane, Gloucestershire Airport, England (2017) Cessna 208 Caravan 1 floatplane (G-MDJE) at Gloucestershire Airport (England) 24May2017 arp.jpg
Floats on a Cessna 208 Caravan 1 floatplane, Gloucestershire Airport, England (2017)


A floatplane (float plane or pontoon plane) is a type of seaplane with one or more slender pontoons mounted under the fuselage to provide buoyancy.


Pontoons for marine industrial uses are usually fabricated from steel. [6] Pontoons as parts of watercraft and aircraft are more typically molded in glass-reinforced plastic. Other techniques include those of traditional wooden boatbuilding as well as plywood over wooden ribs or metal sheets over metal ribs (aluminium or steel), reflecting the prevailing practice in aircraft and boats. In most cases, the decking surface on top of the pontoon is made from glass-reinforced plastic (GRP) or composite lumber. In model building, floats can easily be carved out of solid blocks or laminated sheets of foam. [7] [ failed verification ]

See also

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<span class="mw-page-title-main">Boat</span> Vessel for transport by water

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, shape, cargo or passenger capacity, or its ability to carry boats.

<span class="mw-page-title-main">Multihull</span> Ship or boat with more than one hull

A multihull is a ship or boat with more than one hull, whereas a vessel with a single hull is a monohull.

Naval architecture Engineering discipline dealing with the design and construction of marine vessels

Naval architecture, or naval engineering, is an engineering discipline incorporating elements of mechanical, electrical, electronic, software and safety engineering as applied to the engineering design process, shipbuilding, maintenance, and operation of marine vessels and structures. Naval architecture involves basic and applied research, design, development, design evaluation (classification) and calculations during all stages of the life of a marine vehicle. Preliminary design of the vessel, its detailed design, construction, trials, operation and maintenance, launching and dry-docking are the main activities involved. Ship design calculations are also required for ships being modified. Naval architecture also involves formulation of safety regulations and damage-control rules and the approval and certification of ship designs to meet statutory and non-statutory requirements.

Float may refer to:

Seaplane Aircraft with an undercarriage capable of operating from water surfaces

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.

Watercraft Vehicles that are intended for locomotion on or in the water

Watercraft, also known as water vessels or waterborne vessels, are vehicles used in and on water, including boats, ships, hovercraft, and submarines. Watercraft usually have a propulsive capability and hence are distinct from a simple device that merely floats, such as a log raft.

Amphibious aircraft Aircraft able to land/take-off from both land and water

An amphibious aircraft or amphibian is an aircraft that can take off and land on both solid ground and water, 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 to 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.

<span class="mw-page-title-main">Pontoon bridge</span> Type of bridge

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.

<span class="mw-page-title-main">Trimaran</span> Multihull boat

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.

Pontoon may refer to:

<span class="mw-page-title-main">Floating dock (jetty)</span> Type of dock supported by pontoons

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.

Floatplane Aircraft with floats for use on water

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.

<span class="mw-page-title-main">Very large floating structure</span> Artificial islands used as infrastructure in aquatic environments

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.

<span class="mw-page-title-main">Pontoon boat</span>

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. Better tube designs have allowed builders to put ever-increasing amounts of horsepower on the stern. 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.

<span class="mw-page-title-main">Navy lighterage pontoon</span>

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 Naval 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.

Ocean development refers to the establishing of human activities at sea and use of the ocean, as well as its governance.

Naval Advance Base Espiritu Santo World War 2 base

Naval Advance Base Espiritu Santo or Espiritu Santo Naval Base, most often just called Espiritu Santo, was an 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 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.

<span class="mw-page-title-main">Leyte-Samar Naval Base</span> Major World War 2 base

Leyte-Samar Naval Base was a large United States Navy base in the Philippines on the Islands of Leyte and Samar. The Base was built during World War II to support the many naval ships fighting and patrolling in the South West Pacific theatre of war as part of the Pacific War. A number of naval facilities were built on the east coast of Leyte island. The first base was built at between the city of Tacloban and Anibong Point, a mile north of the city. Headquarters for the Seventh Fleet was built at Tolosa, 10 miles south of Tacloban on Leyte. The bases were on the large San Pedro Bay in the Leyte Gulf which provided safe anchorage for many ships. Due to the lack of dry ground in Tacloban a second base was built on the east side of Leyte Gulf, on the south tip of Samar, on Calicoan Island and Tubabao Island. At Samar, a large Naval Depot was built to support the Pacific War. Samar was about 50 miles across the Leyte Gulf from Tacloban. All construction was done by the Navy's Seabees.

<span class="mw-page-title-main">Naval Base Milne Bay</span> Major World War 2 base in Papua New Guinea

Naval Base Milne Bay, also called Naval Advance Base Milne Bay, was new major United States Navy sea and airbase base built on Milne Bay in Milne Bay Province in south-eastern Papua New Guinea. By spring 1943, the build up of the US Navy to support the Pacific War had caused overcrowding at the ports on the east coast of Australia. To help the Seabee departed Naval Base Brisbane on June 19, 1943 to set up a new base in Milne Bay. Naval Base Milne Bay headquarters was at Ladava Navy Base. The Royal Australian Navy already had a small base in Milne Bay: HMAS Ladava. Australians were able to defend and keep Milne Bay in the Battle of Milne Bay in 1942. Naval Base Milne Bay was built during World War II to support the many ships and aircraft fighting and patrolling in the South West Pacific theatre of war. Ladava Navy Base provided a large protective US Navy fleet anchorage at Gahora Bay next to Ladava. At Naval Base Milne Bay Seabee built large Naval facility.

<span class="mw-page-title-main">Naval Base Okinawa</span> Major World War 2 base

Naval Base Okinawa, now Naval Facility Okinawa, was and is a number of bases built after the Battle of Okinawa by United States Navy on the Okinawa Island of Japan. The naval bases were built to support the landings on Okinawa on April 1, 1945, and the troops fighting on Okinawa. The Navy repaired and did expansion of the airfields on Okinawa. United States Navy Seabee built or repaired the facilities on the island. The bases on Okinawa put the United States Armed Forces only 350 miles from Japan's home islands. Most facilities closed after the war, but some are still in use today in all branches of the United States Armed Forces.


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