Various embodiments of the invention provide a buoy and system for monitoring divers and other underwater objects. In many embodiments, the buoy has capabilities to monitor a diver, obtain position information about the diver and use that information to move itself to an effective range for continued monitoring. The buoy can connect and communicate with a communication device attached to a diver to communicate, position, biometric and other data. In one embodiment, the buoy comprises a propulsion system for propelling the buoy, an acoustic communication module for communicating with the diver and a propulsion controller for controlling the propulsion system to move to the effective range. Other embodiments provide a power generation system using a power generating buoy comprising an inertial weight, an energy converter and a connecting linkage. The system may comprise a single or multiple buoys and can include an electrical storage such as an electrical battery.