"U-Boots" or submarines were diving for a long period of time unnoticed. In Vienna, too, Jews were able to escape discrimination or deportation by becoming “U-Boote”. Being a "submarine" could also mean disguising oneself and assuming a non-Jewish identity.
Life in hiding was challenging – for those in hiding and those who were helping alike. Without registering for ration cards, it was hard to get food. "U-Boote" depended on the help and courage of others – and depended on strong nerves as well. The danger of being discovered was omnipresent. As victims of anti jewish persecution, Jewish helpers faced double the danger.