The ocean is actually an open system so matter and energy move freely throughout the land, the ocean, and the atomsphere, but if this were an isolated sytem this would be completely different. An isolated sytem does not allow any energy or matter to leave keeping what it has trapped inside its system and does not allow any energy or matter to enter. So if the ocean became an isolated sytem, to try and get energy from it, divers and workers would have to go in and extract the energy from the ocean similarily to what they do now, but it would be harder.
Okay so first off an isolated system is when energy and mass can NOT leave the system. wave and tidal energy projects would require us to extract energy from the ocean. (im pretty sure this is correct) hope this helped! (:
