Even luxury can be green.

Microsoft co-founder Bill Gates is ordering the world’s first liquid hydrogen-powered superyacht. Gates reportedly is paying 644-million dollars for the five-deck vessel that will be more than 360 feet long.

The yacht will be called Aqua will be equipped with a gym, spa, beauty parlor, cascading pool, and accommodations for 14 guests and a crew of 31.

The only catch? Hydrogen refueling stations are few and far between, so there’s a diesel engine for back up.

The superyacht is expected to set sail by 2024.