Using the natural power of the rise and fall of oceans to fill a cylinder with seawater and then to use that pressure to pneumatically push an object through a tunnel.
the same type of application in force could create such a vacuum to suck up polution caused from cars and industrial areas from a network of tunnels and filter it.
The wave machine, the wave converter and all the inventions i've seen in that wiki are for harvesting waves natural energy.
what i am thinking of is quite differrent as the australians have devised the way to hydraulically pump water into a basin for desalinization and to power hydroelectric generators when the water is released , however it is not very practical.
what I am thinking of is simply allowing the waters to naturally flow into a hydroelectric plant and release it into a canal that leads back to the ocean in a meandering path.
I have some interesting theories on how the water could enter the resovoir but this brings challenges on how to release it back such as building the powerplant some 1000 ft below sea level on shore and let it rush it, however i am not thinking of a more natural way to have the water return.