Gerhard Linder, captain of the type VIIC unterwasserboot U-579, peered through the periscope at a stream of allied ships. “Mein milchshake holt alle jungen zum yard,” he whispered, referring to the maneuver he used to pull enemy vessels within range of his torpedoes, but at the same time evade their notice. It was known as the milkshake.

Seekadett Jordan Fritzler leaned close. “Well done, captain,” he said in German. "Many of the other cadets served under Captain Grunwald on U-503 before she was lost. We speak of this maneuver over meals, and how well you do it. They speak highly of Grunwald’s milkshake, though. They’re like, its better than yours.”

A British corvette showed her starboard flank to Linder, and he ordered two tubes fired. After several minutes the torpedoes hammered into the corvette, opening two huge holes in her side through which sea water poured.

“Grunwald was a fool, losing 503 the way he did,” Linder finally said. “Nobody has a finer milkshake than I.”