Sea Drone is Solar Powered

I have seen something that is using the waves for propulsion which seems to be more effective as it reduces size and increases payload for the drone.

http:/liquidr.com/technology/waveglider/how-it-works.html#

Very interesting. I expect there are almost always waves in the ocean.

Yes also in the night.

Guess the solar powered one will live of batteries or stay dormant over night, with the danger of not being able to maneuver.

EM's USV is suitable for harbors, rivers and lakes where wave action for propulsion is neglible or intermittent. It is also suitable for very shallow water where a waverider could become entangled or snagged. As an oceangoing vessel a waverider makes more sense so long as it doesn't encounter rough seas.

Ooops. Sorry. My unmanned boat just sunk your $2m yacht, Sue my computer! These things should make great targets but alas, more pollution in the worlds oceans and more secret spies floating around. The cells will soon be powering homes in 3rd world countries and hulls being converted to fishing boats. Nice donation from the tax payer, as usual.

Looks like a light breeze would turn that thing into a flying wing.

Good point. As one objective may be stealth (enough so to mention it on their website) a variable-buoyancy semisubmersible would be virtually undetectable and could dive to a shallow but safe depth during rough seas.