Build a small wind turbine, then build it bigger and bigger.
Put on a generator to get free electricity.
If you want, you can mount the wind-discs above each other on the same drive shaft.
You can also place multiple axes next to each other and connect them together.
I start by using a 1 meter standard 12 M threaded rod, 12 mm nuts and 12 mm ball bearings.
Common woodwork may be used in tests.
A small problem seems to be what kind of generator I'm going to use, thinking of a regular car generator. The problem is that it starts charging at a quite high speed so I have to change the gear.
Keep the weight down to just that it holds together, and learn how to maneuver the vessel.
Then it could be possible to sail with?
A kind of wind turbine boat.
You can not sail against the wind but cross like a regular sailboat.