The pristine lagoon ocean waters surrounding Katafanga island are magically bioluminescent. This means any movement in the ocean waters produces a “glow in the dark’ effect around the movement. This movie “The Blue Lagoon” was shot on location in Nanuya Levu, a privately-owned island in Fiji whose ocean waters are also bioluminescent.
The incredible bioluminescent glow is produced by a reaction that begins when the single celled dinoflagelate organism (plankton) is stirred or moved. The defense mechanism starts a chemical chain reaction that results in a bright blue glow that lasts as long as the plankton is being provoked or stirred into action. This is a reaction that only occurs because a very rare and specific set of nutrients are available in the ocean water to sustain these little "water fireflies".
From an evolutionary point of view, this is an amazing defense mechanism of the plankton. When small fish consume the plankton, they magically start to glow. This glowing light attracts bigger fish who come to investigate the light, and eat the smaller fish.
Several elements had to come together all in one spot for these dinoflagelates to have evolved:
1) A reef or mangrove must surround the ocean water and provide a habitat for specific organism which produces vitamin B12 in large quantities.
2) The opening of the bay to the open ocean had to be narrow enough to keep its waters from being washed out to sea, diluting the dinoflagelate population.
3) The location had to be remote, pristine, clean and without pollutants.
4) The ocean water temperature had to stay consistently warm, and within a very narrow range.
5) The ocean water had to remain calm enough so that most of the saltier water could sink to the bottom and eventually be carried away back into the ocean by mild undercurrents, since the plankton cannot thrive in the saltier ocean water.
6) The population of the plankton natural predators had to remain low.
These plankton provide giant clams with a large source of nutrition. Giant clams achieve their enormous proportions by consuming the sugars and proteins produced by the billions of dinoflagellates that live within them. As a result, they are able to grow as large as 100 centimeters (39.4 in) in length.
Katafanga Island is one of the few places in the world that naturally has all the elements in order for the rare clams to grow this enormous.