Since the 1700s, crossing the equator on a ship has merited an initiation ceremony for sailors who have not "crossed the line" before. Here, aboard the submarine USS Narwhal in 1940, a pollywog is required to crawl through a gauntlet of shellbacks while being sprayed by a firehose. (In the U.S., sailors who have previously crossed the line are shellbacks; first-timers are pollywogs.)