pelican eel

The pelican eel or Eurypharynx pelecanoides is a deep-sea fish rarely seen by humans, though the creatures are occasionally snagged in fishermen's nets.The pelican eel's most notable feature is its enormous mouth, much larger than its body. The mouth is loosely-hinged, and can be opened wide enough to swallow a fish much larger than itself.

http://en.wikipedia.org/wiki/Umbrella_Mouth_Gulper_Eel

http://www.seasky.org/monsters/sea7a1j.html