Plastics and polyethylene are the least expensive materials. Polyethylene is very tough, impact resistant, just about maintenance free and because it is roto-moulded can be made in a variety of shapes, colors and styles. Fiberglass and kevlar boats need expensive molds or plugs to be made first to define the shape of the boat. These molds are labor intensive because the must be built to precise dimensions and need to mate perfectly with other mold sections that make up the kayak. Glass boats tend to be fragile to a certain degree meaning that they do not do well being banged against rocks or docks, do not like to be dragged up on a stony beach and need to be protected form ultraviolet exposure.
Wooden kayaks are almost always custom built or are the material of choice for the home builder.
The hull is coated with fiberglass cloth and resin. After curing, the boat is turned over and separated from the form and bulkheads and decks are installed. Everything is sealed with epoxy for water tightness and strength. This the most labor intensive process of all described. Modern kayak design has produced boats for flatwater, coastal cruising, ocean use and fast moving rivers.