There's a sand beach at Waikoloa on the Big Island. It fronts Anaehoomalu Bay and includes an open stretch of sand, portions shaded by palms, and a series of sandy coves separated by small volcanic rock peninsulas; some filled to the waterline by complex trees.
We spent a quiet afternoon swimming and sunning. At one point, we took a walk away from the populated part of the beach and came upon a group of green sea turtles -- Honu in Hawaiian -- sunning themselves on a shelf of volcanic pebbles hidden behind a lava peninsula.
We didn't want to disturb them, so we kept back a respectful distance and just snapped a few pictures.
There were also several turtles hanging around in the lagoon at the Hilton where we stayed. Several times, we took kayaks out and visited them. There's nothing better than drifting quietly while watching one of these lovely animals flying around beneath you.