A submersible, such as the missing Titan vessel, is a type of watercraft — but it has some key differences from the better-known submarine.
Unlike submarines, a submersible needs a mother ship to launch it.
The Titan's support ship was the Polar Prince, a former Canadian Coast Guard icebreaking ship, according to the ship's co-owner Horizon Maritime.
A submarine can also stay underwater much longer, while submersibles have much fewer power reserves, according to OceanGate, the company operating the Titan expedition, in a webpage seen by CNN that is no longer available.
The Titan has 96 hours of life support, and its dives down to the Titanic wreckage usually last 10 to 11 hours, according to the site — compared to submarines that can stay underwater for months.
Organizations:
Canadian Coast Guard, Horizon, CNN, Coast Guard