These amazing vehicles really are undersea gliders.
Link to NyTimes article: http://nyti.ms/17Q0j7V
Quote from the article:
"There are several models of submersible research drones on the market, but the Gliderpalooza fleet consists of propellerless Slocum Gliders, designed by the Teledyne Webb Research Corporation. They move by adjusting their buoyancy — taking on and expelling small amounts of water to rise and fall in the ocean. Two wings transform this up-and-down movement into forward momentum, propelling the robot in a continuous chain of swoops."