A system is described generally for a water capture structure that is configured to capture wave water lapping over at least one wall of the water capture structure. The at least one wall extends at least above a nominal surface water level and at least one conduit extends downward from the water capture structure. The at least one conduit has a length extending to a depth at which at least one property of water at the depth differs substantially from that of water at the surface. The at least one conduit is configured to provide thermal energy to water outside of the at least one conduit. The at least one conduit has at least one conduit wall.