Oarfish, the probably source of most sea serpent legends. One 17 m long would feed quite a party.

http://news.bbc.co.uk/earth/hi/earth_news/newsid_8501000/8501251.stm

Using a remotely operated vehicle, they caught a rare glimpse of the huge oarfish, perhaps the first sighting of the fish in its natural setting. The oarfish, which can reach 17m long, has previously only been seen on a few occasions dying at the sea surface, or dead washed ashore.

http://www.physorg.com/news185001953.html

Professor Benfield said to his knowledge the oarfish had never before been seen alive in the ocean’s mesoplagic layer (200-1000 meters deep), although there was a possible sighting in 2007 at 765 meters deep off the coast of Africa. He said the fish’s swimming behavior was particularly interesting because it undulated its dorsal fin in waves, and that drove it backwards at “quite a good speed”.