Don't underestimate the damage that some divers can do to ships in harbor. For example, 6 Italian divers went into Alexandra harbor in WWII and put 2 British battleships out of action, changing the balance of power in the Med. There were other attacks like that, too. Since WWII, the techniques, tactics, and weapons for these sorts of attacks have improved dramatically.

Those sea lions have been trained to detect divers and to catch them. They're pretty hard to fool.

"Six Italians, dressed in rather unusual diving suits and equipped with materials of laughably little cost, have swung the military balance of power in the Mediterranean in favour of the Axis".



Sir Winston Churchill, on the sinking of HMS Valiant and HMS Queen Elizabeth by Italian Combat Divers