PP is correct. You can take pictures in the reefs, but not with the stingrays or dolphins.
Stingrays may get confused and try and eat your camera. Not good for you, you could end up with a broken camera and lost pictures. Not good for the stingray...camera inside the body doesn't bode well.
Dolphins by nature are very curious and smart animals. Sticking a camera underwater could grab their attention, and with up to 100 teeth, if they grab on, I'm pretty sure you'll be letting go; and just like the stingrays, causing you to have a broken camera and may nto ever getting it back...and potentially having a dolphin with a camera in it's stomach...well that's a very bad thing for it.
Of the few times I've been to discovery cove, I have purchased a disposal underwater camera to use in the coral reef and lazy river because you still can get such great pictures there. I have also used my own camera for the aviary and other various places around D.C.