Interesting idea to use self propelled robots to provide data on the oceans. They use no fuel to move, they use wave energy. They also have solar panels on the top. The wave gliders can travel to a distant area, collect data, and return to base. One of the big problems with convention methods of collecting data on the oceans is the large costs of placing the buoys (and the cost of servicing them).
Related: Wave Glider – The State of the Oceans – Autonomous Underwater Robot Decides on Experiment Options – Altered Oceans: the Crisis at Sea

Wow this is remarkable. Hopefully one day we can have robots that can make it to the ocean floor in the Mariana Trench.