German Submarines in harbor - Glass negative photogrpah. Public domain.

Photograph shows German submarines in a harbor. Front row (left to right): U-22, U-20 (sank the Lusitania), U-19 and U-21. Back row (left to right): U-14, U-10 and U-12. (Source: Flickr Commons project, 2011)
Title from data provided by the Bain News Service on the negative.
Forms part of: George Grantham Bain Collection (Library of Congress).
General information about the George Grantham Bain Collection is available at http://hdl.loc.gov/loc.pnp/pp.ggbain