It's a story that's captivating the world: the missing five men, who went deep into the Atlantic Ocean to try and get a glimpse of the wreckage of the Titanic.
Oxygen may have run out in the missing Titan submersible but rescuers are still hard at work.
Today, an oceanographer on the dangers and complexities of the mission. 
Featured: 
Arthur Trembanis, oceanographer at the University of Delaware