That is what they are currently doing in Orkney.
I've seen the test rigs up on Eday which feed into the "Surf'n'Turf" project to hydrogen power the internal ferries whilst in dock, it's a small but very impressive demonstration of the various technologies.
The latest floating turbine being tested is really impressive - this single device has been able to reliably produce 7% of Orkney's total electricity needs, and over 25% for short periods.
I still think that tidal power offers the best long term solution, with improved storage technology for peak usage. They are currently building 200MW of battery storage into the grid, 49MW is being built just up the road from me, but I think something more effective will be required in the long term.