Fish Eye Underwater Observatory stands in Piti Bay, reached by a long pier over clear Guam water. Its viewing chamber lets you look out at reef fish and coral without diving, which makes it especially useful for families, non-swimmers, or anyone with limited time.
The experience is controlled and commercial, but the marine setting is real. It pairs well with snorkelling or a coastal drive from Hagåtña, and it gives a quick introduction to the reef life that makes Guam more than a military and shopping stop.