Quest to solve WWII wreck mystery in Plymouth Sound
22 September 2013 Last updated at 14:04 BST
Three years ago sports diver Danny Daniels led a dive team that stumbled on the wreck of a warplane off the coast of Plymouth.
At first Danny thought the wreck was a downed German fighter but, as more wreckage came to light, he realised it was an RAF flying boat - a Sunderland.
The planes were based at RAF Mountbatten in the coastal city during World War II.
He found out that one had crashed off Plymouth in December 1941 - of the 15 crew and passengers only four survived.
Danny developed an obsession with finding out the cause of the crash, going through Met Office archives to find out more about local weather conditions and visiting relatives of a survivor.
With exclusive underwater footage of the wreck site, Inside Out South West follows Danny in his quest to solve this World War II mystery.
Inside Out is broadcast on BBC One South West at 19:30 BST on Monday, 23 September and nationwide on the iPlayer for seven days thereafter.