Is all "dark tourism" immoral? Five wealthy people set off on a trip to see the wreck of the Titanic at the bottom of the sea. But now they have gone missing.
Race against time to rescue lost Titanic sub
Deadly depths: Contact with the sub was lost just one hour and 45 minutes into its descent to the wreck site. Glossary
Titanic - The RMS Titanic was the largest ship afloat at the time and it is the deadliest cruise ship disaster in history.
Experts - Someone who knows a lot about a particular subject.
Chernobyl - The disaster, in 1986, involved a meltdown at a nuclear plant in Ukraine.
Immoral - Outside of what most people in society think is right and fair.