The night before we left Hawaii for home, I did a night time Manta Ray Snorkel with Kona Honu Divers (www.konahonudivers.com) and it was great (while Janet went shopping). Their boat leaves from Kona and takes us to an area they call "Manta Ray Heaven", which was just offshore from the airport. Basically they (and about 6-7 other boats) shine lights down from small rafts that the snorkelers hang onto, and they have lights on the bottom with the divers that point up. The lights attract plankton, and the plankton attracts fish and the Manta Rays. We saw 22 Manta Rays that night which is well above the normal number. The images here are screen captures from the video (with permission) that I purchased from LiquideHi.com. It was well worth buying the video they make of your actual snorkel/dive! The snorkel/dive lasted about 4 hours.