On a night dive in the Philippines several years ago, I had an opportunity to do a "fluoro" night dive. Atlantis Dive Resort rented blue underwater flashlights and yellow filter shields that went over divers' masks. Geared up, I set off into the night. The blue light was very dim and the dive was much darker than a normal night dive.
I suddenly felt like I was in a neon video game with the underwater world transforming into vibrant greens, reds and yellows. A bright, glowing light snaked across the sand, and on closer inspection, it was an eel that was vivid green.