Waikiki Aquarium
A small aquarium right on the Waikiki shoreline focused entirely on Pacific and Hawaiian reef life, which means kids see the same fish they might snorkel with an hour later. Hawaiian monk seals live in an outdoor habitat and are the highlight for most children. There is a giant clam collection, a jellyfish gallery and a shallow outdoor touch tank. The whole visit runs about an hour and it is walkable from most Waikiki hotels, which makes it an easy rainy-morning pivot. Partly open air, so a poncho helps in a real downpour.