Riviera Maritime Media reported a recent demonstration by Saab showing their Sabretooth AUV’s ability to perform tasks like inspection and maintenance, and return to a subsea docking station for recharging and video download. Quite amazing advance that will allow ROVs/AUVs to stay at depth for dramatically longer periods.
Blue Robotics’ BlueROV2 is also capable of being “permanently submerged” at >800m, which MBARI and The Quest Institute working together with others have done with their unit: