In this respect U-boats were like any other naval vessel in any other navy -- or any civilian vessel, for that matter. (Or any school, or any office building.) While the boat has an official complement of so-and-so many crew members, there are myriad reasons that, at any given time, there will be a few more or a few fewer men actually on board. Men get sick, they go overdue on leave, are transfered to another vessel at the last minute without a replacement, or someone is added to the crew for a special reason (e.g., a war correspondent). Official complement figures only describe the number of men a vessel is intended to carry; in practice (and on larger vessels in particular), the actual number of men on board is almost always slightly different.

-----------> AH