Hi Guys ,
Here is a great site about the U boats(listing over 900 insignia/emblems) and everything else to do with them .
www.uboataces.com
U-boat insignias and emblems were popularly sported by U-boat crews during the war. Emblems and insignias were an expression of individualism or they could also sometimes be representative of some sort of feature of meaning connected to their boat. Propaganda and superstitious influence also came into play, with some sporting the clover for good luck, or cupid for a good shot. One of the more well known emblems is the golden horseshoe by Otto Kretschmer. The horseshoe was welded with the opening facing downwards for good luck, and ironically, the destroyer that sank his boat, also bored a horseshoe for good luck, but it was facing upwards.
Before the war, U-boat numerals were painted in large white letters about 1.5 meters tall on the conning tower. At the outbreak of war, however, these numeral markings were discontinued and all boats were painted an overall neutral gray in order to keep the enemy guessing about the deployment of the U-boat force. It didn't take long however, before U-boat crews began adopting insignias and emblems as a means of self expression and individualism.
In addition to U-Boat emblems, each graduating class from U-Boat academy also chose an emblem. The crew of 1936 chose the Olympic Rings, in reference to the 1936 Olympic Games in Munich. An upright dagger through a wedding ring was chosen for the crew of 1937, and was characterized as "First win, then marry!". Even U-boat flotillas had emblems. The 7th U-flotilla adopted the snorting bull after Gunther Prien's boat while the 9th flotilla had the laughing sawfish as its emblem.
However, not all boats had emblems, while some boats had more than one emblem. For example, a boat could display its flotilla emblem, the graduating class emblem and the boat's individual emblem. When a new commander took over a boat, he would just add his own emblem rather than replace the existing emblem and risk losing the old luck. U-boat insignias were also worn on uniforms, sewn onto caps and even imprinted on items such as mugs and badges.
With the advent of the true submarine, such as the Types XXI and XXIII, which spent most of their time underwater, these boats rarely surfaced and thus together with it, the colorful naval tradition of the U-Boat insignias began to fade out.
Here is a couple from the site
Nap