Floats (also called pontoons) are airtight hollow structures, similar to pressure vessels, whose air-filled interior makes them buoyant in water. They are most often used to make up the multipart hulls of trimarans, small open catamarans, and floatplanes (a kind of seaplane). Their main purpose is to supply buoyancy, not storage space. The other principal domain of use for pontoons is in marine engineering and construction—shipbuilding, marine salvage, dredging, port facilities, and so on. In such applications, pontoons are sunk, positioned under objects needing raising (such as sunken ships being recovered for their scrap metal value or to clear channels), and then pumped full of air with air compressors, raising the object. Pontoons are also used to build things like pontoon bridges and floating piers. Such applications make them a useful tool for combat engineers and civilian engineers alike.
Pontoons for marine industrial uses are usually fabricated from steel plate and sheet. Pontoons as parts of watercraft and aircraft are more typically molded in glass-reinforced plastic. Before the 1970s, glass-reinforced plastic was rare; older 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 model building, floats can easily be carved out of solid blocks or laminated sheets of foam.
- The Cruising Multihull. 978-0070698680: International Marine/Ragged Mountain Press. 1996. p. 45. Retrieved 2009-05-27.