The depths of the ocean are so unexplored that many cannot possibly comprehend what it is that lurks beneath the surface; it's darkest reaches are home to some of the greatest examples of predatory perfection. Bio-luminescence is just a bi-product of being an apex predator from way down below, though it seems to be a help when hunting in lighter waters as well.

Geranguas, being such a large dragon, knows it's a bit of a downside when it comes to finding prey big enough to sate a great hunger. Though every now and then, a shark happens to get a little too large for it's environment and an even greater hunter strikes from below.

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Artist's Page: http://www.furaffinity.net/user/patto/
Original over here: http://www.furaffinity.net/full/16842177/