German navy used submarine minelayers according to the Dutch magazine Marineblad dated 1915-1916 no. 4

An item referred to a statement of a certain Mr. Archibald Hurt in the British newspaper Daily Telegraph reporting that Germany used considerable submarine minelayers. The submarines were fitted out with a watertight compartment in which some lines of mines were stored. Although relatively small were the mines of sufficient explosive strength. Is the mines to be laid was the compartment closed and filled with water and then the mines mechanically thrown out.