Hydrogen as a fuel

Probably not - you have no way of cooling the fuel to the temp required to keep it liquid. It was our only choice - besides leaving the biz. When the liquid becomes gas it expands to 600x.

CNG is more likely = 3600psi and can be quick filled. But you need to have a ready source at the marina - I can't see a tanker truck dispensing it.

The alternatives are no better - barrels of DEF and/or scrubbers on the stacks.

The Spanish company Navantia is currently building AIP submarines, the S-80, that, instead of carrying H2 in tanks, uses green ethanol which is easily available in many countries now, and a reformer that splits it into carbon and hydrogen onboard the sub, which is used in the fuel cell stack. The carbon is dissolved into seawater. Much safer way of handling hydrogen. Navantia's “BEST” AIP (Bio–Ethanol Stealth Technology) (spsmai.com)

A lot of companies are investing in Hydrogen, for me if you want to get rid of fossil fuels it is the future.
Unless a magic thing appear like BITF and we can make fuel from garbage.

FPT is advanced in both a Hydrogen cell (this more advanced) and a Hydrogen fuel.
So is Cummins and Yanmar.
Another Italian company from Bologna has also developed a smallish very efficient hydrogen engine.

Again for BIG ships, not for recreational boaters

I would question recreational boats carrying fuel in high pressure tanks. The lack of maintenance and inspection would have consequences.

Mr. Lürssen mentioned Freudenberg Group as Lürssen's partner for the hydrogen/fuel cell technology.

Another company called zerocenergy has a 136 m superyacht called project Grace on their projects list. Same project?
https://zerocenergy.com/projects/

Biodiesel 100 is better choice.

Not yet..... The regulatory writing is on the wall though. Here's someone doing some testing out of his own pocket.......

https://www.forbes.com/sites/billsp...d-superyacht-bill-gates-is-reportedly-buying/

The green eco-terror revolutionaries will destroy the west in their attempt to demonize fossil fuels. They won't succeed, but by then 75% of the world's population will be dead or dying.