Which World War II submarines could dive deepest?

Which navy had the World War II submarine with the greatest crush depth?

A French design may lead by stated depth, while deep American wartime dives and differing national measures prevent a simple ranking.

Published test, operating, and claimed crush depths are not always directly comparable. The initial answer places American and German submarines at the front of the wartime comparison, with British boats close behind. A later correction identifies a French design with a greater stated depth, while US submarines made very deep emergency dives off Japan. Those claims answer different questions about designed limits and demonstrated wartime performance. The ranking remains cautious because national figures and actual emergency dives measure different things.