I was on a night snorkel in Bermuda about 10 years ago, that went with a dive operation that was located on the beach at Snorkel Park. Pretty sure this operation is no longer there.
However, if you find an operator that runs these tours, I can tell you ours was amazing. We had lights on our heads of course, so you could see underwater. We saw a huge variety of sealife, including cuttlefish and a sleeping octopus!