If you want to go on the Jolly Pirates (snorkeling) definately book ahead. My friends and I almost didn't get on the boat because it's really popular. Plus, if you book ahead you get 15% off (go to their website
www.jollypirates.com to book)
Another thing you might like if you like to snorkel is DePalm Island. An artificial island with snorkeling, restaurant, and many other things.
Baby Beach is a great place to go and relax too. The water is very clear and you can wade out about 50 yards and still have it be up to your waist. There is also some pretty good snorkeling there to.
One beach to stay away from if you like to be in the water is Moomba Beach. It is really muddy on the bottom, but if you like to just read on the beach then it is a great place to go!
Hope this helps! Enjoy your honeymoon! And like cindyo said you will love Aruba! And don't forget to post your story on "My Aruba Story"