A system (1) for operating a subsea sensor field (2), comprises an automated underwater vehicle—AUV (10) and a subsea service station (13). A sensor (11, 12) in the sensor field (2) comprises a permanently installed base unit (11) and a removable control unit (12). The AUV (10) moves control units (12) to the service station (13) for charging and updating, and then back to the base units.