In Kona, I usually stay at the Kona Seaside. I would wake up insanely early and go get coffee from somewhere on Alii drive and watch the spinner dolphins out in the bay. 100's of them out playing most every morning. I'd watch them from the seawall by the old green church.Absolutely love Hawaii. Been to the Big Island many times, and Oahu.
I snorkeled Kealakekua Bay one year. It was the most incredible display of spinner dolphins I've ever seen. Could have been 1000 of them. They were layered 100ft down, all the way, encircling.... Incredible.