Complex sentence: The ballerina makes a mistake in uncovering where Armstrong and Sherman are hiding on the ship, the wrong crates are fired on when already dangling over the pier, and Armstrong and Sherman are able to escape by jumping overboard and swimming to a Swedish dock.
Split into simpler sentences: The ballerina makes a mistake in uncovering where Armstrong and Sherman are hiding on the ship. They escape by jumping overboard and swimming to a Swedish dock.