The Battle of Britain Five Months That Changed History, May—October 1940 by James Holland (z-lib.org).epub

but in fact the majority of the ship’s number had been German and Italian
prisoners. The Captain, twelve officers, forty-two crew, ninety-one British
soldiers, and 713 POWs went down with the ship. But Günther was not to
know.
On 6 July, U-47 returned to Kiel, drawing alongside the quay with
‘66,587 tons’ painted on the conning tower above the snorting bull, and
with a pennant depicting every one of the ships sunk on the patrol fluttering
in the wind.
Despite the still comparatively small size of the U-boat arm, the
submarines were beginning to cause havoc in the Atlantic. In the narrow
confines of the Channel, however, lurked other dangers: mines, divebombers
and what the British called E-boats. The Germans preferred
another name: Schnellboote. Fast boats. And they were. Deadly fast.