Inflatable boats may have rubber floors, either plain or inflatable, or they may include steel, wood or aluminium sheets for rigidity. The tubes are made of rubberised, synthetic sheets of Hypalon or PVC to provide light-weight and secure buoyancy. The tubes are often constructed in separate sections, each with a valve to add or remove air, to reduce the effect of a puncture.
Some inflatable boats have an inflated keel to create a “groove” along the line of the hull improving the hull’s wave cutting and turning performance. Due to the lightness, it is easy to cause an inflatable boat to start hydroplaning, thus making it faster than the engine would allow when the hull is operating in displacement mode.
A growing use for inflatables is for white water rafting and kayaking, as well as in river, lake and ocean touring. Professional-level rafts and kayaks have existed for many years; since the late 1990s, more affordable inflatable rafts, kayaks and canoes have been developed by European and North American companies. Typically these inflatable boats contain no rigid frame members, so they can be deflated, folded and stored in compact bags.
Inflatable liferafts were also used successfully to save crews of aircraft that ditched in the sea; bombing, naval and anti-submarine aircraft flying long distances over water being much more common from the start of WWII. The PBY Catalina made by Consolidated Aircraft and Canadair seems to have been the first aeroplane to have had an inflatable life boat aboard, first as optional, later as standard equipment. A later version of that inflatable was pressurized by a gas cylinder rather than by mouth. A wire connected to the plane opened the cylinder valve in the inflatable after the life raft was thrown into the water.
Until the middle 1950s inflatables were still rafts in civilian use, hand paddled but the outboard motor came into use in the early 1950s. (The outboard motor was invented in 1909 by Ole Evinrude.)
Also in the 1950s, the French Navy officer and biologist Alain Bombard was the first to combine the outboard engine, a rigid floor and a boat shaped inflatable. The former airplane-manufacturer Zodiac built that boat and a friend of Bombard, the diver Jacques-Yves Cousteau began to use it, after Bombard sailed across the Atlantic Ocean with his inflatable in 1952. Cousteau was convinced by the shallow draught and good performance of this type of boat and used it as tenders on his expeditions.
The inflatable boat was so successful that Zodiac lacked the manufacturing capacity to satisfy demand. In the early 1960s, Zodiac licensed production to a dozen companies in other countries. In the 1960s, the British company Humber was the first to built Zodiac brand inflatable boats in the UK.
Some inflatables have inflated keels whose V-shape help the hull move through waves reducing the slamming effect caused by the flat hull landing back on the surface the water after passing over the top of a wave at speed.