So there was this rich Sim, he saw a sea stack and decided to live there. Problem was, where to build a house.
He bought in sand, built up a reasonable patch around the sea stack and made his own town. Impressive?
Well not really. He didn't get to live on the island, as his ship sank just short of the shoreline.

Alas, you can use it now to build your own neighborhood. Plenty of space for beach lots, and three isolated lots for secret societies/specialty lots for your mysterious Sims.
The three isolated lots are pictured below, and as you can see the extensive shoreline for beach lots.



Additional Credits:
Travellersside for his tutorial on terrains.
Eaxis, SimCity4, Photoshop