Diver Mitch,
You'll have a blast in Guam, the diving is second to none. The Grotto in Saipan is a must dive, but hit the stairmaster before, its 140 steps down and back in full gear, its well worth the pain.
There are lots of things to do topside, if you want some good info about the island when you get there, stop by Shooter's bar in Hagatna and talk to the owner "Ric", he's been living on Guam 23+ years, he will give you the straight story about Guam. Tell him "Big Jim" sent you.
Hey Jim,
Thanks for the heads-up. I'll look up once I get there.
Mitch