This is an oarfish - one of a group of long bony fish found in tropical and temperate waters throughout the world. One species (Regalecus glesne) is capable of reaching 17m (56ft) in length.
Lengths of up to 36ft are common, and oarfish are thought to be responsible for many sea serpent legends. They are rarely seen alive and little is known about their behaviour.
Read more about them here: http://bbc.in/VAhG19