Special Warfare insignia was created in 1970.

Enemy surface ships are the main target of submarine warfare

The Submariner's insignia for most of the world's navies are the "dolphin" badge (U.S. Navy - Submarine Warfare Badge). The typical insignia denotes a pair of dolphins (traditionally dolphin fish (mahi-mahi), though bottle-nose are also used) abreast the bow of a submarine. Dolphins were chosen as they are considered not only good luck for submariners, they are also constant companions while at sea in areas where they're around.

For the U.S. Navy, the Enlisted Dolphins are silver or pewter; Officers are gold.

There is an enlisted example on my supervisor page.

Germany hoped that submarine warfare would lead to war.

Anti submarine warfare