Hearing my wife scream underwater..........we were snorkeling some blue holes on Andros Island in the Bahamas and were side by side floating on the surface. There was a cut in the coral to my side that was a bout 7' wide and acted as an entrance into the hole and saw a huge southern stingray swim into the hole from the opening. As I watched it swim in, I knew that it had to swim right in front of our faces on it's way out and held my ground, apparently my wife knew this also, screamed into her snorkel and did the porpoise "backpedal". Just wish she held on for some better photos!
On a side note regarding the lionfish.......true, we've seen them in several places in the Caribbean, but recently in Aruba, we ate at a place called Reef and Beef which serves lionfish on the menu and often sells out. A bit more expensive than the grouper, but heard it is very good.