its an island. Lots of sand, like Hawaii, but out in the water is a different story. You really can't get out beyond the break in most places, so you never get to water above your waist.
Im sure there is one or two beaches that you can swim in, but I didn't go to any. I did go to an enclosed part that was pretty cool.
Guam is like the Japanese people's Hawaii, but it's nowhere near as nice. There are some strip clubs, places to eat, and they do have scuba, including places to get certified. All in all, Guam sucks.
Air Force base has a decent golf course that's probably not open to the public.
The history of Guam is a little interesting, but you don't need to go there to see it. They barely did anything to preserve any of it. Oh yeah, it's expensive.
I recommend Cebu, Philippines if you want a beautiful place with way more beautiful women that is cheap. Similar air travel time and will be a better overall experience. Yes, they speak English in Guam and use the dollar, but it's not worth it in my opinion.