Yeah, the sea’s already doing the work, you just have to tap it. Think of a simple oscillating paddle on a submerged boom that swings with the waves – the motion turns a small gear. Couple that with a lightweight keel that keeps the boat upright, and you’ve got a self‑propelling system that needs only a motor‑driven winch for occasional steering. Keep the hull aluminum or composite, use recycled PVC for the boom, and wire the gear to a low‑power DC motor that powers a tiny propeller only when you need extra speed. The trick is to design the paddle so the water’s push is always in the right direction; a few rubber bands or springs can lock the paddle in place at the peak of each wave. That’s about it – wave energy, a little mechanical advantage, and no fancy electronics.