Deep sea rescues have a mixed track record. The Pisces III is one that succeeded

Divers begin to open the hatch of Pisces III as she breaks water under the John Cabot after being hauled from the Atlantic seabed off the coast of Cork, Ireland. (PA Images via Getty Images)

The clock is ticking in the all-hands-on-deck search for the tourist submersible that went missing during a deep-sea dive to the Titanic shipwreck on Sunday.

The vessel has five people on board and, according to the U.S. Coast Guard, a dwindling oxygen supply of 40 hours.