12 December, 1943, after 08.26: The oil slick left by U-172
.Taken by Radioman Burke from the same position, this picture shows how right Obermaschinist Walter Gerke was when he refused to endorse the hasty repair of fuel bunker 7 in Saint-Nazaire. The bad welding has already given way, plaguing U-172
with a tell-tale oil trail escaping from her leaky fuel bunker. This also induced constant shifts in her displacement, thus impairing her underwater handling, a probable cause for her involuntary broaching at 09.27.