The boats are built plastic efficient.
Wood has for millennia been the most prevalent boat building material. Animal skin and canvas have used skin boats with a frame of wood. Glass fiber reinforced plastic boats came in the 1950s.
A 3.5 to 4 meters plastic boat weighs at best below 100 Kg and a kayak around 5 meters weighing 25-30 kg. Reinforced plastics (composites) are not easy to recycle. There is currently no economically recoverable way.
Hull fabric of polyester into a kayak and a SOT / SUP, weighing about 300 grams, compared to 25 kg in a plastic hard shell kayak, so it's very little plastic. The canvas can be separated from the body when the kayak / boat must be recycled.
Polyester fabric is a fantasktiskt material that is strong and light. It is not affected by water but is sensitive to sunlight. Primer to protect against UV light and topcoat used is an acrylate.