Every year, more than a million people get to swim with the fishes in a marine ecosystem located on the southeast coast of Oahu, 10 miles east of Waikiki. Hanauma (or curved bay) Bay is a former volcanic crater that became a protected marine life conservation area in 1967. Since then, it’s become an underwater park for snorkel enthusiasts, swimmers and anyone desiring to see more than 400 species of Hawaiian fishes including Hawaii’s state fish the humuhumunukunukuapua‘a, turtles and other marine life.
Hanauma Bay Nature Preserve is open year-round, except for Tuesdays, Christmas and New Year’s Day. Plan to arrive as early as you can or wait until the crowd trickles out in the mid-afternoon. During summer, the state park opens at 6 am and closes at 7 pm. It closes at 6 pm in winter.
https://www.hawaii.com/oahu/attractions/hanauma-bay/