A strange creature allegedly filmed by underwater drillers in the deep ocean on April 25 has sparked intrigue and controversy on the Internet. Theories about the mysterious animal range from a jellyfish to an unknown marine version of the Loch Ness monster to a whale placenta.

Neither the source of the video nor the location where it was filmed have been revealed, leading some people to suspect a hoax.

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Others note that the video seems authentic, and that a hoaxed video would likely be much more dramatic. Scale in the video is unclear, and without more information about the drill site (for example the diameter of the pipe the animal moves in front of), it's impossible to know exactly how big it is.

There's no doubt that there are strange and mysterious creatures in the ocean depths — and even ordinary creatures that have been mistaken for extraordinary ones. In one famous case, a Japanese fishing trawler pulled up what appeared to be the carcass of an unknown sea monster off the coast of New Zealand in 1977.

It looked like a dinosaur, with a long neck and what might be flippers or fins. Photos of the creature still appear in books about unexplained mysteries, though the animal was identified as a basking shark that had decomposed so badly that it was unidentifiable.

There are a few clues to this creature's identity. First, it should be noted that (contrary to some sensational news headlines) the object isn't really a "blob" at all, but instead composed of what appears to be a fairly thin membrane. It more closely resembles a satin bedsheet than a blobby monster.

This suggests that the animal has no skeleton and little or no musculature; whatever it is, it's not a big, strong monster but likely something fairly fragile.

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It also has no obvious mouth or sensory organs. Second, it moves very little (if at all) under its own power; the form mostly moves along with the current (and the waves created by the remotely operated vehicle mounted to the camera).

Several experts are pretty sure they know what it is. According to one Web site, "Southern Cross University marine biology lecturer Dr. Daniel Bucher told ninemsn the giveaway was its sex organs. 'In last the 30 seconds or so you start to see more of the structure, these pendulous tubes with four or five whitish structures and some branching between them, which look to me like the gonads of a jellyfish,' Dr. Bucher said. 'I have no idea what species it would be, but if I had to say it would be a very unusual shape deep sea jellyfish.'"

The favored candidate for the species is Deepstaria enigmatica, a poorly understood and rarely seen specimen found in deep water. According to the Marine Species Identification Portal, the Deepstaria enigmatica has a bell (top canopy membrane) that is "remarkably thin, broad, delicate, a rather flat inverted bowl when relaxed" and reaches about 60 centimeters (2 feet) in diameter.

While the creature in the video appears much larger than 2 feet, it could be an unusually large specimen — or it could simply mean that the very few specimens found so far were unusually small. Whatever it is — Deepstaria enigmatica, unknown monster or something else — the animal is long gone, and the mystery will remain.