The Beach
Why this might seem obvious, one of the main reasons, if not the main reason to be in Oahu is to see the beautiful beaches. You also don't have to spend a fortune renting snorkeling equipment each day you are at the beach. You could pick up relatively inexpensive equipment for sale at an ABC store or for the best value we recommend buying some cheap snorkeling set from Amazon beforehand and just throwing it in your suitcase. In regards to beaches, Waikiki Beach is a must and yes, you could snorkel and see fish and turtles in Waikiki.
Hawaii State Art Museum
US Army Museum of Hawaii
2131 Kalia Rd. Honolulu HI 96815
Pearl Harbor National Memorial