Even those of us who would never step foot inside a submarine have probably wondered what the exit procedure is - and whether there only one way out.
If you have ever wondered what happens if you need to get out of a submarine - your questions have been answered.
The story started back in 1851, when German submarine inventor Wilhelm Bauer and his crew were trapped inside their submarine, Brandtaucher.
The Brandtaucher plummeted unexpectedly to the seafloor, 16 metres deep, and had the crew waiting hours for rescue.
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In an attempt to evacuate, Bauer reached up to a valve which resulted in water pouring in and flooding the submarine.
The risky move turned out to be the trio's ticket to freedom as they all propelled out through the hatch door, like 'the corks of champagne bottles,' as put by Bauer.
The event recorded Bauer, Witt, and Thomsen as the first three submariners ever to successfully escape a submarine.
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Thankfully nowadays, submarines provide a means of escape in a semi-organised manner, i.e. they don't need to flood the entire boat in order to get out.
Instead, submariners can escape through inner doors or hatches that seal tightly behind them. After swimming out, the outer hatch is sealed against the ocean and the escape trunk is drained, allowing another group of submariners to follow suit.
According to Wired.com, submariners today wear full-body waterproof suits called SEIE suits, which is an acronym for Submarine Escape Immersion Equipment.
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The equipment - pronounced 'sigh' - are brightly coloured fabric pods that allow submariners to break free from their plunged vehicle. Each sailor is paired with a partner, and clear plastic panels act as viewports.
Submariners can pop up to the water surface and the suit makes like a flotation raft, provided they can reach a hatch among the wreckage. These suits are an essential piece of kit to prevent death from high levels of CO2.
The road to today's submarine escape solutions wasn't always straightforward, but the experiences and close calls of past submariners that have led to the solutions of today.
Later retrieved from its mud hole in the ocean, the Brandtaucher is conserved in a museum in Germany where it's recorded as the oldest submarine ever recovered.