The hawksbill sea turtle, spotted off the Solomon Islands, is the first reptile seen to exhibit biofluorescence.
The creature was spotted in July by marine biologist David Gruber, who was on a nightdive hoping to capture footage of biofluorescent sharks and coral reefs.
Gruber, based at City University in New York, described the endangered turtle as looking like 'a big spaceship gliding into view', National Geographic reported.
In exclusive National Geographic footage, the turtle glows green and red, although it is thought that the red could be down to algae growing on the reptile's shell.
Scientists are yet to work out why the turtle exhibits this unusual feature.
Alexander Gaos, director of the Eastern Pacific Hawksbill Initiative, said: '[Biofluorescence is] usually used for finding and attracting prey or defense or some kind of communication.
It can also be used to attract a mate.
Scientists said it may be difficult to study the newly discovered glowing phenomenon in the hawksbill turtle because they are so endangered
He added that it may be difficult to study the phenomenon in the species because there are so few left.
Worldwide, the species' population has declined by nearly 90 per cent in recent decades.
Biofluorescence occurs when an organism absorbs light, transforms it, and re-emits it as a different colour.
It should not be confused with bioluminescence, seen in algae and jellyfish, which occurs when animals are light sources in themselves.
In biofluorescence, specialised fluorescent molecules in the animal's skin are stimulated by high-energy light, such as blue light.
They then lose a fragment of this light energy and release the rest at a lower-energy wavelength such as green, seen in the turtle.
The unusual type of light can only be produced – and seen by humans – when the organism is being illuminated by an external source, such as by a light bulb.