Golf course
Although a bit weird, a golf course at sea might be a good way for earning money.
Prerequesites
- A cheap way to create "land"
- More infrastructure, like a really luxurious hotel and restaurant
Advantages
- Golf courses that have an extra feature (being next to the Sea, being the first golf course ever, having the most rich members) tend to have much higher fees than the average ones. A golf course at sea will attract rich people and media attention.