These rays are the largest sting rays, and can grow to at least 2 metres across (and possibly larger). While harmless, they do have a venomous barb on their tails which could inflict a serious wound if you got yourself in the wrong position relative to it. When threatened, they apparently raise their tails over their backs like a scorpion.
They are large enough to have relatively few predators, and most of those are sharks and killer whales. Seeing one is (for me) an extremely exciting event. The poor camera work and heavy breathing on these two videos (both taken on the same dive, on 31 December 2011, but of different rays) attests to my excitement. The visibilty was not stellar on that day – perhaps 4 metres – but because the rays stir up a lot of sand with their wings and mouths (snuffling for worms and white mussels in the sand) it’s significantly less here.
There’s some good detail on these creatures, which are surprisingly widely distributed, on (dare I say it) Wikipedia. Click here.