If there is one group I get excited about seeing while snorkeling around St. Croix, it is the stingrays. I have seen both southern stingrays (Dasyatis americana) and spotted eagle rays (Aetobatus narinari), though a few other species do live around the island.
The southern stingrays are usually sedentary, seen lounging on the sea floor. They are either in plain sight, or partly buried in the sand. This is not much of a disguise for a snorkeler who knows what shapes in the sand to look for. Sometimes you can also spot them while they are feeding - you will first see a plume of sand in the distance, and as you approach, the stingray will be concave over the sand, trying to suck up some prey.
When you swim close, they generally are not too perturbed. I do not try to touch wild stingrays - while unlikely, I don't want to risk getting stung. Also, I don't want to spook them too much, I'd rather get to watch them and take some photos. This little stingray had a wingspan of only about one foot, and started turning around as I dove down to take a photo. The sea floor was too deep for me to stay more than a few seconds, though, and he slowly swam away as I surfaced. My friend and I followed him for a while before some fish caught our eye.
The spotted eagle rays are a bit more elusory - never sitting still, they fly through the shadows. I don't always see them, even after week long trips of snorkeling at various beaches. This trip, at Fredericksted pier, we saw two large eagle rays float between the posts. They did not alter their speed or their course, even as the three of us swam toward them. It was a surreal moment.