When I arrived in Grenada the water temperature was 82 deg F. Today it is at 85.5. and is getting warmer each day. I guess that's what make the hurricanes.
The warmest water I've been in this year was in the Gulf Streem that was 84 deg F. Since then all of the islands have been near 80 or 82 deg.
In the past I've only been to Grenada in November or December and then the water temps were 76 deg F.