Water Generators are not a new thing. Indeed...some wind gens have a water gen option. They have never been all that popular as:
1. You need to be underway for them to to work and cruisers spend 80-90% of their time at anchor.
2. Fouling and loss issues.
I am seem to recall that the company you are thinking of is actually out of business with a slew of customer issues left in its' wake.
EDIT: I am NOT referring to Duogen which is a wind/water model. While there have been some reliability issues with those (and some production upgrades from the original), most people seem to b happy with the in-water performance and with the service when they have a problem. In air performance however is lackluster. $3500 is a lot to pay for one imho!