The top snorkeling spot on Oahu is Hanauma Bay. There is an admission fee. Marinelife conservationists would remind you to please refrain from bringing bread as fish food. The only acceptable food offering is found in local grocery stores. Feel free to stop by one and stock up on frozen peas to feed the fish of Hanauma Bay.
Life guards are on duty.
Reef islands have long been the homes of peoples like the Polynesians and Micronesians in the Pacific and the Maldivians in the Indian Ocean. The coral reefs help protect the islands and provide the protected calm waters. Please remember that coral reef islands, especially those close to sea level, are not very stable. Coral can be damaged, and possibly the entire coral colony can be killed by human trespassing. Furthermore, coral is razor sharp and can jeopardize human safety.