Based on

Movies like Titanic's Lost Sister (1996)

An account of Dr. Robert D. Ballard's exploration of the wreck of the Britannic in September 1995. Britannic, the sister-ship of the Titanic, was sunk after a mysterious explosion while serving as a hospital ship during World War One. Ballard sets out to relocate the wreck and attempts to prove once and for all whether it was a German mine or torpedo which inflicted the fatal damage.