According to Commander von Forstner's account of the incident, the wreckage remained under the water for about 25 seconds until an explosion sent some of the debris flying up.

It is said that along with the debris, a creature described as a "gigantic aquatic animal" resembling a crocodile was seen, which quickly disappeared from sight.

On 2 September, at 11:55 am, it encountered the armed English steamer Olive Branch, 85 nautical miles (157 km; 98 mi) north-by-northeast of North Cape, Norway.

The shells detonated Olive Branch's cargo of munitions, which it had been carrying from England to Arkhangelsk, Russia, and the subsequent explosion so badly damaged the nearby U-boat that it sank along with the steamer.

[8] An alternative description of the event states that when the ammunition detonated, a truck carried as deck cargo was blown into the air and fell from a great height on the U-boat, sinking it.