As the sun goes down on warm water oceans throughout the world, a secret war is waged by the subtle, insidious enemies of all good things that swim. The enemy is patient, clever, and well-equipped. And all we landlubbers ever see are the scars.

The Cookiecutter Shark is a small shark, just under two feet long, that spends the daytime a mile or deeper beneath offshore waters in temperate oceans. It lurks, and it waits for darkness to fall.

As the sun sets and the ocean waters settle into dusk, the sharks rise nearly to the surface on silent fins. Unlike most sharks, the Cookiecutter is capable of hovering in the water without swimming, due to adaptations in its body structure and the density of its liver.

It is the black stealth helicoper of the marine world. On top of its ability to hover silently, the Cookiecutter has small bioluminescent lights (photophores) on its underside that shine softly, blending in with the ambient light that filters down from the moon and the stars above. The entire underside of the shark is covered in these glowing lights, making it effectively invisible when viewed from beneath, with one exception -- a dark band around its neck, where there are no lights.

From below, all any other marine animal will see is a small, dark thing floating in the water, something that looks like a fish just sitting there waiting to be eaten. The rest of the shark blends in with the ambient light and cannot be seen, even by animals with good eyesight and even at close distances.

When a potential predator swims up to take a look or a bite, it is in for a surprise. The Cookiecutter will wait unmoving until the other animal gets close, and then it will burst forward and attach itself to the animal, usually to the animal's side.

The Cookiecutter has a suctioning mouth that locks onto the animal. It pulls its tongue back to create negative suction, sealing the mouth lock. The shark then clamps its circular band of teeth into the animal's flesh, vibrates its jaw like an electric knife, and saws a hole out of its victim.

Sometimes it takes a chunk of flesh, sometimes it cuts out a whole plug and exposes the animal's innards. The cut is smooth and clean and professional. Once it has its pound of flesh, the shark will release and vanish back into the dark waters.

No animal is safe from the Cookiecutter. Whales, dolphins, other sharks, large fishes, seals, stingrays. The Cookiecutters attack them all, throughout the oceans. Emaciated whales have been found beached, riddled with Cookiecutter scars. Circular gouged wounds have been seen on countless animals in the oceans, and found frequently on fishing catches in warm ocean waters. Off Hawaii, practically every single adult dolphin bears Cookiecutter scars.

The Cookiecutter rarely comes in contact with humans due to its nocturnal habits and the fact that it lurks in deep offshore waters during the day. However, it has been documented attacking undersea photographers in packs, biting the rare swimmer around Hawaii, and shipwreck survivors have reported waking to find clean, deep Cookiecutter bites in their bodies.

In the 1970s, several US submarines were forced back to base after holes were cut in their sonar arrays, causing them to leak oil. At first the Navy feared a secret Soviet weapon, but after investigation they learned that they were in fact under attack by Cookiecutter sharks. All submarines after that had their vulnerable sonar pieces coated in fibreglass to stop the sharks. In the 1980s the sharks launched another round of attacks on submarines, this time attacking rubber-sheathed electrical cables, which again had to be covered with fibreglass. They have damaged oceanographic research equipment and undersea communication cables.

The next time you look at a tranquil ocean scene, remember the dark menace that lurks beneath, waiting to rise up and wage its secret, stealthy war against all that swims.

See the link below for a picture of the Cookiecutter Shark, also known as the Luminous Shark (it has the strongest known bioluminesence of any shark) and the Demon Whale-Biter. For a picture of the wouds it makes on other animals (specifically a tuna in this shot), go here:

http://www.peninsulatotaltackle.com.au/getattachment/Articles/January-2010/Tuna-Tales!/IMG_0541-Web.JPG.aspx