Autonomous wave gliders are relatively small, autonomous (unmanned) sea craft that sail at the sea surface and get their forward propulsion from wave energy. They can be very useful for long-endurance data collection missions. Their published performance typically reports average forward speed and control up to sea state 3. But what happens to them in higher sea states, like sea state 5 and 6? In particular: Does their average forward speed plateau with increasing sea state (level off at a constant mean speed as sea state increases)? Are they still able to navigate toward a specified waypoint? Can they still get their own position from GPS at sea state 5 and higher? Can they still report their position by radio or satellite comms? Is their navigation and/or communication out of operation during the time of high sea state, tossed at sea until seas become calm again? Is the surface body submerged most of the time at high sea states? Thanks.