"I haven't gone over the prospectus in detail, but where do they get potable fresh water from? And power?"
Fresh water is likely from wells on the island. Even though you're surrounded by salt water, fresh water, in the form of rain, is less dense than salt water.
When it rains and the water percolates down through the ground it forms a fresh water layer on top of the salt water.
If that weren't the case, Hawaii wouldn't be habitable by the number of people that are living there.
Power? Probably a distribution cable from the mainland.