For most people though, the GoPro will be the camera of choice. It’s versatile and relatively inexpensive. But make sure you think about how to mount the camera before taking it on an underwater trip. Snorkelers should avoid chest, wrist and mask mounts because they’re difficult to aim.
My wrist mount captured great video of my fellow snorkelers but rarely captured any whales. I found the best option is a pistol grip—a short stick you can attach the camera to. And I would suggest using just one camera at a time—for your own sanity. I took some stills with the GoPro, but I wasn’t impressed.