This afternoon I helped out on a boat trip to recover one of the sea gliders from South Cove.
There are in fact two science teams here this year using sea gliders. The particular glider I went out to help collect had an acoustic instrument deployed that can detect krill. Another glider is being used to conduct survey missions underneath ice shelves.
The gliders have an internal bladder that can be inflated and deflated to displace water. When the glider bladder is inflated the glider it is buoyant and rises and when the bladder is deflated the glider gradually sinks. The wings and fins allow the glider to move and make progress as it rises and sinks.
The gliders transmit their position back to base via a satellite link.