Ever since explorer William Beebe descended into the depths in a metal sphere in the 1930s, marine biologists have been astounded by the number and diversity of glowing animals in the ocean. Yet few studies have actually documented the numbers of glowing animals at different depths. In a new study in Scientific Reports, MBARI researchers Séverine Martini and Steve Haddock show that three quarters of the animals in Monterey Bay waters between the surface and 4,000 meters deep can produce their own light.