From PMEL: A new device developed by NOAA PMEL engineers is currently contributing to the NASA Salinity Processes in the Upper Ocean Regional Study (SPURS) in the Atlantic Ocean.
Two of these "Prawlers (Profiler + Crawler)" were developed and deployed as part of the study. Once released, the instrument descends while taking a CTD profile, meanwhile sending real-time information to the surface buoy. Once it reaches it's bottom depth, it uses power harnessed from wave-motion to crawl back up the line, eliminating the need for multiple sensors on the mooring line. You can watch the SPURS Prawler Data in real time at the following link: http://ferret.pmel.noaa.gov/spurs/UI.vm.
Links: NASA SPURS study
PMEL News Release.
Image from NOAA PMEL: http://www.pmel.noaa.gov/images/headlines/spurs.png