Hi lemurs2,
....so what will be of most use to you is knowing what scuba temps to anticipate.
To put it in perspective, below is a piece, in part, from my "Ask RSD" column in "Rodale's Scuba Diving":
"Have you ever been out on the street in the spring or fall and noticed people wearing everything from shorts & T-shirts to full coats with hats & scarves, all apparently in comfort? Well, things are no different underwater. This comfort is highly variable among individuals depending on such factors as percentage of body fat, age & tolerance to thermal discomfort. Other determinants, like how many dives a day over how many days you are planning, are also important. When you ask "What wetsuit should I wear?, you'll get answers ranging all the way from "just a bathing suit" through "7mm full."
The question is better asked: "What water temps can I anticipate at my destination?" You'll receive a pretty accurate answer to this, and then can decide what's best for you based on your personal thermal comfort needs.
It's always a good idea to come thermally prepared, just in case."
That having been said, expect mid-Aug Cayman Islands scuba temps of ~85F +/- a degree. Remember that liveaboard diving is different than land-based, where with mid-80's water temps some divers may be able to get away with a skin. On the Nekton Rorqual you'll be diving for a full week and most days can get in 4-5 dives. As the number of dives increases, the demands on thermal reserves become substantial.
Personally, I'd take a 3 mil full. If you get a bit too warm during a dive, you can always let some water into the suit. It's much harder to warm up.
Have fun.
DocVikingo
