Plastic

Plastic kayaks are normally rotomolded polypropylene. In the rotomolding process, a hollow mold is heated and beads of polypropylene are added to the interior of the mold. The mold is rotated as the beads melt and stick to the inside surface. Once the beads have melted and have been dispersed, the mold is cooled, and then opened, leaving the molded kayak for finishing.

Polypylene kayaks are tough, seldom damaged much by rocky bottoms of rivers or beach. They tend toward being soft, and heavy. They are also among the cheapest of kayaks. Repairing a rotomolded kayak is tricky, but possible with a heat gun and some plastic. Fortunately, they seldom seem to need repair.

Kayaks built by rotomolding are for the mass market. Building the mold is expensive, and the manufacturer must get their costs out of the process by either charging high prices (latest style whitewater kayaks) or by selling a large number of kayaks over several years - recreational kayaks.