Probably because there have been rescues of explorers nearly running out of air while trapped in a submersible. https://www.dailymail.co.uk/news/article-122205

Probably because there have been rescues of explorers nearly running out of air while trapped in a submersible. https://www.dailymail.co.uk/news/article-12220565/The-nerve-shredding-tale-two-British-engineers-sat-stranded-Atlantic-seabed.html https://www.dailymail.co.uk/news/article-12220565/The-nerve-...