Here's the trick if you want to know what's happening underneath the pristine Guam waters: Atlantis Adventures Guam Submarine Tours. First, arrive at the docks at Aqua Marine World, where a charter boat will take you to the dive site in Apra Harbor in 15 minutes. Then, settle into a 65-foot submarine for a 35-minute dive under the sea. See tropical coral reefs and colorful fish swimming by, 40 meters deep, while staying dry and cool in the air conditioned submarine. You'll be shuttled back to the shore the same way you came after this unforgettable experience.