This is an easy question.
1) There are no overwater SPG properties that provide a good value.
2) To use SPG points, transfer them to miles and fly somewhere you'd enjoy. Don't get too hung up on going to an SPG property for a free continental breakfast.
3) That said, St. Regis Bora Bora is nice. Go to a non SPG property in Maldives. Both places are pretty easy to get to with miles.