[roflc0ptic]

Take a long tube with an osmotic filter on it. Put it in the sea with one end out. Pressure is going to fill the tube up, no, just like a snorkel? Probably back up to sea level, possibly minus whatever force reduction caused by the filter? Boom, water filtration with no expenditure of energy.

It may be wrong but it really isn't "obviously delusional."

[postalrat]

You forgot the part where the water in the pipe is less dense and would be pushed up.