Several different knives have been issued to German frogmen in the past decades. In the GDR, there were at least four different designs, three made locally at the 'Messerschmiede Mühlhausen', one made in Hungary. They all have serrated back edges, the blade design varies from a dagger-like style to an AK-bajonet-type.
The FRG Bundesmarine Kampfschwimmer used the Barakuda, another Bowie-type blade with a saw edge on the back. There also is a nonmagnetic (Titanium?) design called the 'SPIRODAG', of
which I have neither pictures nor other info. Their current issue knife is the Eickhorn ACK, which is a modified AK bajonet design with a hollow handle. All this info comes from a special issue of the German weapons
magazine 'Visier' titled 'Militär-Messer' ISBN 3-89715-211-8.
Hope this helps,