Good day Jasch and thank you for your question! This is a very good question! We generally stay in the sub for 4-6 hours although the deeper dives can be stretched out to 12 hours. In terms of Legroom, I would say it is comparable to an average size car although this will vary from sub to sub. Stretching your legs is possible in our sub although you will have to be mindful of your fellow passengers. I heard that James Cameron undertook a lot of Yoga to prepare him for his journey inside Deepsea Challenger which due to the subs deep diving capabilities had a much smaller sphere. Pilots also require a medical certificate to prove that they are medically fit to pilot a submersible.
Depending on the nature of the dive it can be mentally demanding – for example working on cliffs in high currents demands a lot from the pilot. Working with some camera crews who want to get the perfect shot or even filming bioluminescence with the main lights off can exact a toll on the team. At the end of 6 hour dive you certainly feel the effects! For these reasons we limit the dives to around 6-8 hours. Obviously, humans need to visit the bathroom and the longer we stay down the greater the likelihood of someone needing to answer natures call. Food is also a big driver!
The image below shows the pilots legroom. The seat cushions have been removed during maintenance, The Mission Specialist would sit on the left and the scientists/guest would sit on the right.
This picture shows a fairly common seating arrangement although this will vary across manufacturer.
The old Alvin Submersible layout
UBoat Worx Submersible
