Yesterday I went to Ahalanui Beach Park. Locals simply call it the Hot Pond. It's a man-made lava pool right next to the ocean. What's special about it is that the water temperature is around 91-95 F. There are many small fish in it and swimming here is like swimming in a spa, just better because you can see the ocean and palm trees and be outside. The water is volcanically heated from below. It's a mixture of ocean water and spring water, so it's not as salty as the ocean. I had my mask and snorkel with me and it was awesome to snorkel in this pool. The water is very clear and the fish are so tame they are not scared of humans at all. It's not a refreshing swim, but this experience can only be enjoyed on Hawaii's Big Island (since it's the only one with active volcanoes).
Nice park area with many trees
The hot pond
Snorkeling in crystal clear water
View from the pond