Good propganda flick:
Snorkels created several problems for their users. A U-boat with a snorkel raised was limited to six knots to avoid breaking the tube, and its sound detection gear was deafened by the roaring of the air being sucked down the tube. Most dramatically, snorkels were equipped with automatic valves to prevent seawater from being sucked into the diesels, but when these valves slammed shut the engines would draw air from the boat itself before shutting down, causing a partial vacuum which was extremely painful to the ears of the crew and sometimes even ruptured eardrums