How do I start acquiring the Initial investor/sponsor for the Initial Project feasibility (Stage 0)?

If you have invented something of importance, you might try patenting it first, before sharing the ideas. Otherwise I would discuss with experienced professor or researcher who knows how to obtain grants, publish findings, etc., or other funding source might be energy companies. You assume also that you might be allowed to install a prototype in ocean, but likely need permission, permits, etc. for that, and how to move electricity to land for storage or transmission. Also assess how safe is system to marine life, people? How susceptible to storm damage? A sponsor/investor is going to want many of these questions answered first. If developed on University time as an employee or student, it may also have some rights to invention. You may need some legal advice. If University or another agency has a dedicated marine experiment station, that may be a good option for trial installation, monitor results, etc. A licensed engineer may need to review or certify plans for safety, consistency with laws and liability issues.