First off, when most people think manta ray, they think sting ray. They're not the same thing. Although the mantas have a long pointy tail, it's not dangerous. Secondly, sting rays (at least in my mind) are not nearly as giganto-huge as the manta rays I saw last night. Manta wingspan is anywhere from 10-20 feet, and when they're swimming right next to you, it seems way bigger. However, they don't have teeth, and though they could fit several humans in their mouth, they aren't interested in people (at least as food). They're not scared of them either. So when mantas see the lights they come gliding under you, gracefully flapping their wings, and then backflip up, scooping in all the plankton close to the lights, showing you their belly (and wide mouth) as they fly by. Just take a look at the video below and you'll see what I mean. And no, I'm not zooming in. These things were less than an inch from me.
This first video was taken very shortly after we entered the water and before we positioned ourselves above the SCUBA divers, which turned out to be fortuitous since their lights didn't lend themselves to good video.
And this video gives you a sense of the melee that ensues once all the lights are in place. Fish join the party, and then the bubbles start floating up, and it gets very busy. Then there are those 20-foot wide creatures circling all around you. I had to remind myself to keep breathing.