The idea here is to buy a panamax (or bigger) sized cargo ship, strip it out, and cover the entire thing in turf.
With a few added bumps and whatnot, you've got yourself an offshore golf course. Balls would have to be biodegradable, or maybe magnetic and buoyant, so that they stick to your hull.
Indoors, there would be mini golf, crazy golf, and so on, right through the ship. It would be completely packed with golf stuff.
You could also have smaller ships, also turfed with golf holes, that are deployed from bays within the mothership. They'd sail out, and you'd have to hit them from afar over the water. You'd never have the same hole twice!
Why? If you can think of a better way to waste so much money, I'd like to hear it. Until then, I'm saving up for this.