WHAT IS THE PROBLEM WITH HAVING MOVING PARTS IN THE WATER?
[/b] Water, especially sea water, causes corrosion in many engineering materials. The replacement and maintainance of these parts is very costly, especially in applications of relatively low power density. With no moving parts in the water, there is much less to corrode, as cheap, resiliant materials can be used. Also, the lack of complex machinery below the surface makes installation and inspection much easier. If there is a system with a large vertical extent, and which rotates, then there are large differential forces caused by the differing water speeds at different depths. These cause engineering and operational difficulties.
