I don't have a picture but...

[Aigtbootbp]

When doing a night dive in Cozumel last Sept. we had these worm looking things come straight for our lights. They "swam" in a spiral motion, looked like a corkscrew was coming at us. As long as we had lights on they went straight for them. We shut them off and swam for a short distance, when were turned them back on the worms were gone.
So, what the heck were these things?
Oh, they looked just like big earthworms.

 

[designbysue]

Maybe bloodworms. If there is a basketstar nearby, you can use your light to direct the bloodworms to the star and watch it catch them.

 

[smellzlikefish]

I encountered a swarm of bristleworms one night that acted and looked similar to what you describe. I assume it was some kind of mating aggregation by the way they seemed to clump together. As I was in a shorty wetsuit and bristleworms can leave a stinging sensation, I stayed well clear, especially as they swam at my lights.