Navy Lighterage (NL) pontoons is type of pontoon developed in World War II by the US Navy and used by naval construction teams (Seabees) and specialized US Army combat engineers on invasion beaches and shallow harbors or harbors where the facilities have been destroyed or do not exit, establish docks, wharfs, barges, floating cranes and other floating units off beaches and harbors where needed.
The concept for NLPs was first discussed in 1935, but it was in 1940 that the US Navy took the idea seriously and began development with testing just before the US entered World War II. The Dieppe Raid in early 1942 showed that the idea of seizing a port in the face of modern coastal defences was either costly or impossible. The US Navy saw the vital importance of being able to building their own port facilities and naval construction teams trained and dedicated for just that role. The US Army soon followed with their own units.
Construction
The NL pontoons are constructed of flotation units of welded steel square boxes, that are assembled like children' wooden block toys which are connected together by special angle iron pieces, called stringers and the flotation boxed and stringers are held together by special iron wedge pins. The NPL flotation blocks come in two types. The main floating box unit is rectangle-square and is 5 ft × 5 ft × 7 ft (1.5 m × 1.5 m × 2.1 m), the majority of NL pontoon units are constructed using these. The second box is similar to the first NPL flotation box, only it is curved upward on one side, and these boxes are used to make a bow on the front of an NPL barge when required, similar to a coal or grain barge like you see on rivers.