This gorgeous bay filled with crystalline green-blue waters lies within a collapsed volcanic cone along the southeast coast of the Island of Oʻahu. One of the world’s most impressive natural aquariums, the bay teems with marine life and is guarded from rough surges by a sheltering stretch of coral reefs at the mouth of the bay.  Boatloads of brightly colored fish frequent the bay, as do the endemic Green sea turtles (called Honu). President Obama snorkeled here with the First Family on one of his Hawaii visits. The bay is closed on Tuesdays to let the fish rest and recuperate (no joke). Parking can be tight and the early bird truly gets the worm. Plan on a half-day trip minimum and pack loads of sunscreen.