Ocean gliders

*"AUVs." One hears much less of these aautonomous underwater vehicles than one hears about aerial drones, probably because they haven't killed anybody (that one knows of).

http://www.nrl.navy.mil/media/news-releases/2012/navy-researchers-sail-down-under-to-study-internal-tides-with-auvs

(...)

"Ocean gliders are becoming one of the Navy's main tools for collecting data on the internal structure of the ocean for assimilation into ocean models. A glider is a long-endurance autonomous underwater vehicle (AUV) used to collect ocean data; it surfaces periodically to transmit data via satellite. Gliders are capable of collecting numerous types of data, including currents, temperature, salinity, pressure, and optics...."