Kits are available. Use duct tape as a temporary measure. Plastic boats can only be repaired by the manufacturer. Folding boats need special care and should never be dragged on the beach. Sharp rocks and barnacles will destroy the hypalon hulls.
Sand is particularly destructive to joints and ribs.
The sand lies between the skin and the frame and abrades the protective surfaces allowing water to enter the wood or for electrolytic erosion of the aluminum.