You may think the vibrant blue shown in the photo above is part of a scene from Avatar or Tron, but it is in fact naturally sourced. Some organisms are able to produce light and these are said to be bioluminescent. Bioluminescence has many valuable functions within the animal kingdom, such as illumination, distraction, warning, mimicry and attraction.
A spectacular example of this emission of light is in coastal areas when there are mass accumulations of plankton. The colour is produced by an enzyme called luciferase and a pigment called luciferin. Oxygen in the shallow marine environment reacts with luciferin and luciferase acts as a catalyst during the process. Oxyluciferin is produced in an electronically excited state and in returning to its ground state it emits a photon of light.
The glow is completely harmless to humans, and can prove quite entertaining as the following video shows. Here the surface is being disturbed, prompting the algae to give off their iridescent blue glow.