Ocean gliders propel themselves through changes in buoyancy.   By alternately reducing and expanding their volume, gliders can descend and ascend through the ocean using very little energy.  Unlike other automated ocean sampling equipment, such as Argo floats, gliders have wings, a rudder and a movable internal battery pack allowing them to move horizontally in a selected direction while sampling.  Essentially this means that the gliders’ horizontal position is controllable, allowing researchers to determine where the glider goes and permitting precise sampling of particular oceanographic features and profiling across strong currents.  Being unmanned and fully-submersed, the ocean gliders can work around the clock in all weather conditions continuously sampling the water for temperature, salinity, dissolved oxygen, chlorophyll and turbidity.  They are remotely controlled and navigate by waypoints, fixing their position via the Global Positioning System (GPS) through Iridium satellite.  Each time the glider surfaces, collected data and new waypoints can be relayed via satellite.  Two types of gliders are used as part of the IMOS Ocean Gliders facility; Slocum gliders and Seagliders.