Floats which can sometimes be called a pontoon are basically an airtight structure is hollowed out, which is very similar to a pressure vessel was designed to create and provide buoyancy within water. The overall principle application was in watercraft hulls as well as floating piers, aircraft floats, and even pontoon bridge construction which does include marine engineering applications like salvaging.

There are different objects that use floats which are normally called pontoons.
Floats will often make up the various parts of the hulls of trimarans or tri-toons and catamarans and often help to give buoyancy to houseboats, floatplanes, and seaplanes. They are can be used for floating piers, floats that are anchored to the seabed for dockage or recreation, and even pontoon bridges. They can also be used in marine salvage and ship building and they can be used while they are uninflated and then pressurized to raise up sunken objects.
In most popular usage, the overall term of pontoon may refer to any of the below objects that are used to make a nautical float.
The pontoon boat is a flat type of boat that does rely on a nautical float to be able to be buoyant. The most common type of boat designs for a pontoon is going to be the catamaran which floats on two pontoons or the trimaran which is floating on three pontoons. In most parts of the world, the pontoon boat is used as way to ferry cars and people across lakes and rivers.
Located in New Zealand and Australia, they use the term pontoon to describe a type of anchored platform or raft that is used to drive into the water from. The pontoons are often located and various beaches, especially where swimming classes are taught as well as lake shores, but it is only during the summer months there.
The floating dock is also known as a floating jetty or floating pier is normally a ramp or platform that is supported above water by nautical floats. It is often joined to the shore using a gangway. This pier type often stays in a fixed vertical type of relationship with various types of watercrafts secure to it.
The pontoon bridge which can be called a floating bridge will use shallow drift boats or floats to be able to support a continuous type of deck for people and vehicles to travel on. Most pontoon bridges are just temporary and are often used during civil emergencies and during war times.
Floatplanes which are also called pontoon planes are a type of seaplane that has one or multiple skinny type of pontoons that are mounted underneath the plan to help provide buoyancy in the water for landings and during takeoff. The floats are often made from steel. The pontoons that are part of a watercraft as well as the aircrafts are normally made from a glass reinforced plastic. There are other types of pontoons that can be made from plywood which are laid over wooden ribs or even metal sheets over a metal rib, which is similar to the practice of boats and aircrafts.