No, this is not complete science fiction or a story by Jules Verne.  The Odyssey AUV (Autonomous Underwater Vehicle) can actually  hover in place.
Folks from MIT’s Autonomous Underwater Vehicles Lab have created the Odyssey IV, another AUV in the latest of a long line of AUVs.  The Odyssey IV can go down to a depth [...]

The robot called the Autosub 6000 is being deployed by the National Oceanography Center in Southampton UK.
It will run for 1,000 kilometers at a time on lithium polymer battery packs.  It should have used the difference in water temperature as its energy source like the robot glider from Woods Hole.
The Autosub 600 will be sent [...]