Wikipedia
Kneeboarding is a discipline of surfing where the rider paddles on his or her belly into a wave on a kneeboard, then rides the wave face typically on both knees. The typical kneeboard is between five and six and a half feet in length, with a wide round nose and constructed of Glassfibre over a polyurethane foam core. Kneeboard designers however are known for their wild experimental excess and so most modern materials including various aerospace elements such as Titanium alloys (for fins), carbon fibre and kevlar in epoxy matrices are not unusual. Modern kneeboards may have a rubber pad for the rider's knees, preventing undue wear of the knees, also preventing slipping to help the rider maintain control. Kneeboarders also typically use swimfins and an ankle surfleash.
Kneeboarding popularity increased markedly with the release of the surf movie "Crystal Voyager" by the most prominent of kneeboard riders, Californian, George Greenough. The music of Pink Floyd's "Meddle" combined with spectacular slow-motion images by Mr. Greenough, filming inside the tube whilst surfing a "spoon" kneeboard, changed surfing's direction, influenced board and fin design and earned him a Palme d'Or for short film at the Cannes film festival in the late 1960s.
The advantage of kneeboarding is the ability it gives the rider to deal with tube rides that might require too quick of a take off for a standup surfer or bodyboarder to get into and might get too tight or steep for a stand-up board surfer to deal with. Being closer to the Face of the wave, the feeling of speed is more enhanced, with a resulting increase in excitement. It seems that kneeboarding is where the best of the skill sets unique to each of the surfing disciplines "comes together".
Kneeboarding is an aquatic sport where the participant is towed on a buoyant, convex, and hydrodynamically shaped board at a planing speed, most often behind a motorboat. Kneeboarding on a surf style board with fin(s) is also done in waves at the beach. In the usual configuration of a tow-sport kneeboard, riders kneel on their heels on the board, and secure themselves to the deck with an adjustable Velcro strap over their thighs. Most water ski kneeboards do not have fins to allow for easier surface spins. As in wakeboarding or water skiing, the rider hangs onto a tow-rope. The advantages of kneeboarding versus other tow-sports seems to be an easier learning curve and a sense of being closer to the water when falls occur.