It is a fun thought. Probably far less efficient and slower than current propulsion, but no moving parts is a big plus. Small drones that patrol the ocean for

It is a fun thought. Probably far less efficient and slower than current propulsion, but no moving parts is a big plus. Small drones that patrol the ocean for long times would be a cool application. Move a bit until the batteries are nearly depleted, float around to recharge, and then resume moving.