A deep-sea rescue mission is under way for five people on board the missing craft, which had submerged to explore the wreckage of the Titanic. The submersible went missing on Sunday morning, less than two hours into the expedition to the wreck, which lies more than two miles below the surface of the North Atlantic.

1. Hull is made out of five inches of carbon fibre, allowing it to withstand high pressures at the wreck of the Titanic.
2. Propelled by four electric thrusters - two horizontal, two vertical - allowing it to travel at speeds of up to three knots.
3. Pilot steers using a modified video game controller.
4. Weights allow Titan to sink 2.4 miles below sea level, and can be offloaded so that it returns to the surface.
5. The toilet is separated from the rest of the crew by a thin curtain, and provides a spectacular view through the 21-inch viewport.
6. A titanium cap is bolted on to the hull before the expedition, sealing passengers inside until they return to the surface