Dolphins are bright in a couple of ways. They appear to be quite intelligent. One thing I noticed during this encounter was how much clicking noise the dolphins were making. It was more or less continuous. The clicking is basically the dolphin’s sonar, and it’s how they keep track of each other and their surroundings. It’s very precise and accurate.
Also, the markings of spinner dolphins in Hawaii differ from those elsewhere, which tend to be a more uniform gray. Hawaii’s spinners are only gray on top, with a pearly band along their sides, and a bright white underside, as prominently displayed by the dolphin in the center of the lower photo, showing off for the camera (possibly).