German submarine U-30 (1936)
Summary of raiding history

Date
Ship
Nationality
Tonnage
Fate
3 September 1939
Athenia
United Kingdom
13,581
Sunk
11 September 1939
Blairlogie
United Kingdom
4,425
Sunk
14 September 1939
Fanad Head
United Kingdom
5,200
Sunk
28 December 1939
HMT Barbara Robertson
Royal Navy
325
Sunk
28 December 1939
HMS Barham
Royal Navy
31,100
Damaged
11 January 1940
El Oso
United Kingdom
7,267
Sunk
16 January 1940
Gracia
United Kingdom
5,642
Damaged
17 January 1940
Cairnross
United Kingdom
5,494
Sunk
7 February 1940
Munster
United Kingdom
4,305
Sunk
9 February 1940
Chagres
United Kingdom
5,406
Sunk
8 March 1940
Counsellor
United Kingdom
5,068
Sunk
20 June 1940
Otterpool
United Kingdom
4,876
Sunk
22 June 1940
Randsfjord
Norway
3,999
Sunk
28 June 1940
Llanarth
United Kingdom
5,053
Sunk
1 July 1940
Beignon
United Kingdom
5,218
Sunk
6 July 1940
Angele Mabro
Egypt
3,154
Sunk
21 July 1940
Ellaroy
United Kingdom
712
Sunk
1 August 1940
Canton
Sweden
5,779
Sunk
16 August 1940
Clan Macphee
United Kingdom
6,628
Sunk

Question: How destructive was U-30 in encounters not ending in a sink?
Answer: U-30 damaged Gracia that weighed 5,642 GRT and HMS Barham.