German submarine U-155 (1941)
Summary of raiding history

Date
Ship Name
Flag
Tonnage
Fate
22 February 1942
Adellen
United Kingdom
7,984
Sunk
22 February 1942
Sama
Norway
1,799
Sunk
7 March 1942
Arabutan
Brazil
7,874
Sunk
14 May 1942
Brabant
Belgium
2,483
Sunk
17 May 1942
Challenger
United States Navy
7,667
Sunk
17 May 1942
San Victorio
United Kingdom
8,136
Sunk
20 May 1942
Sylvan Arrow
Panama
7,797
Sunk
23 May 1942
Watsonville
Panama
2,220
Sunk
28 May 1942
Poseidon
Netherlands
1,928
Sunk
30 May 1942
Baghdad
Norway
2,161
Sunk
28 July 1942
Barbacena
Brazil
4,772
Sunk
28 July 1942
Piave
Brazil
2,347
Sunk
28 July 1942
Bill
Norway
2,445
Sunk
30 July 1942
Cranford
United States
6,096
Sunk
1 August 1942
Clan Macnaughton
United Kingdom
8,088
Sunk
1 August 1942
Kentaur
Netherlands
5,878
Sunk
4 August 1942
Empire Arnold
United Kingdom
7,045
Sunk
5 August 1942
Draco
Netherlands
389
Sunk
9 August 1942
San Emiliano
United Kingdom
8,071
Sunk
10 August 1942
Strabo
Netherlands
383
Sunk
15 November 1942
Ettrick
United Kingdom
11,279
Sunk
15 November 1942
HMS Avenger
Royal Navy
13,785
Sunk
15 November 1942
USS Almaack
United States Navy
6,736
Damaged
6 December 1942
Serooskerk
Netherlands
8,456
Sunk
2 April 1943
Lysefjord
Norway
1,091
Sunk
3 April 1943
Gulfstate
United States
6,882
Sunk
24 October 1943
Siranger
Norway
5,393
Sunk

Question: How destructive was the U-155 submarine?
Answer: U-155 sunk 26 ships totaling 126,664 gross register tons (GRT), and damaged one warship of 6,736 GRT.