I'm not so sure. For a wind turbine a lot of maintenance can be done without any additional vessel / cranes. If you need to do a major component change you do i

I'm not so sure. For a wind turbine a lot of maintenance can be done without any additional vessel / cranes. If you need to do a major component change you do it with a similar vessel to the ones which installed the turbine. For a subsea tidal turbine you'd need some frame or similar to land the tidal turbine onto, you'd need to clean it before anyone could access it for the maintenance etc. Generally speaking if you have something subsea it should be designed to be maintenance free as recovery costs are so high (like subsea oil and gas production systems).