How long can a Submarine stay underwater?

 How long ago were Submarines invented? How are Submarines able to sink? How does a Submarine make air for its crew to breathe? Have you started your FREE TRIAL of Who Smarted?+ for AD FREE listening, an EXTRA episode every week & bonus content? Sign up right in the Apple app, or directly at  Get official Who Smarted? Merch: tee-shirts, mugs, hoodies and more, at Who Smarted? For more information about our other projects, including bespoke branded podcasts and series for your company, check out  Atomic Entertainment.