Isn't that the human torpedo?

Indeed it is - an Italian Siluro a Lenta Corsa (Low Speed Torpedo) to be precise. Its crews referred to it as 'maiale' or 'pig.'

A number of them were used quite successfully in a raid on Alexandria harbor in December 1941, whereby teams of frogmen slipped into the harbor, attached mines to a few British warships (including two battleships), and then detonating said mines. All the divers were captured, but they managed to badly damage a number of warships.