Does a submarine's inside diameter get visibly smaller on deep dives? I recall a show where they tied a string taut from wall to wall and once deep under water the string
![Mastering Physics Solution, "A research submarine has a 10-cm-diameter window that is 9.0 cm thick. - YouTube Mastering Physics Solution, "A research submarine has a 10-cm-diameter window that is 9.0 cm thick. - YouTube](https://i.ytimg.com/vi/Q__gnye1JAA/maxresdefault.jpg)
Mastering Physics Solution, "A research submarine has a 10-cm-diameter window that is 9.0 cm thick. - YouTube
How do submariners know how thick the ice is above them to gauge whether they can safely surface through it? - Quora
![Submarine! The Classic Account of Undersea Combat in World War II: Beach USN (Ret.), Cap. Edward L.: 9780743487993: Amazon.com: Books Submarine! The Classic Account of Undersea Combat in World War II: Beach USN (Ret.), Cap. Edward L.: 9780743487993: Amazon.com: Books](https://m.media-amazon.com/images/I/51+3e3uitiL._AC_UF1000,1000_QL80_.jpg)