In 2005, the Los Angeles-class submarine USS San Francisco collided with an undersea mountain while sailing at full speed.
In order to maintain stealth, the San Francisco had not been operating its active sonar and was traveling too fast to make effective use of its passive sonar. The crew, meanwhile, were not utilizing the most up-to-date undersea navigation charts, and the outdated charts they were using did not indicate the presence of the mountain formation.
When the vessel rammed into the mountain, the collision injured just about the entire crew — some of them quite severely — and took the life of one sailor on board.
The crew was able to rescue the situation from becoming a true calamity, however, and one of the sailors was able to flip the switch that causes the submarine to carry out an emergency surfacing despite having two broken arms. The crew was then able to improvise enough to get the submarine moving, and the vessel eventually arrived safely in Guam.