Gel coat on canoes and kayaks is there purely for esthetics (colour and smooth finish). With larger fiberglass powerboats that might sit in the water most of their life, the gel coat resists osmosis. Canoes and Kayak spend a very small percentage of their life in the water. For this reason, osmosis is not a concern for canoes and kayaks. Gel coat repairs are purely esthetic. Spider cracks my have structural damage behind them. They should be assessed.