water & sewer how/where

I recently was looking at the florida keys and key west on google earth and wondered about -#1 fresh water ? #2 sewer/waste. ? Pipes along the highway from the mainland, to/from key west with branches to all the little developed islands on the way ? Thats like 75+ miles. OR many/couple little w/s plants and a lot of wells/septic systems, i don’t think there is freshwater under, even 500feet, under those little plots of land, in the ocean. How is it done, it would be a lot of pipes!?

http://www.fkaa.com/our_water_source.htm

I work as a Union Laborers and have sewer and water installation
Experience. Most homes in the Florida Keys are very close to
The water table. Any fresh water would have to be piped
In. Sewage from business would have to be held in underground
Storage tanks if no sewage lines existed. If sewage lines were
Available, intreated sewage could be pumped ( most sewage
Lines are gravity flow ) to a sewage treatment plant. Treated
Water could the conceivable be dumped into the ocean. Solids
Would be trucked and used as fertalizer.