She was fitted with a Schnorchel underwater breathing apparatus in November 1944.
German Type VIIC submarines were preceded by the shorter Type VIIB submarines. U-1055 had a displacement of 769t when at the surface and 871t while submerged. She had a total length of 67.1m (220.1feet), a pressure hull length of 50.5m (165.7feet), a beam of 6.2m (20.3feet), a height of 9.6m (31.5feet), and a draught of 4.74m (15.55feet). The submarine was powered by two Germaniawerft F46 four-stroke, six-cylinder supercharged diesel engines producing a total of NaNPS for use while surfaced, two AEG GU 460/8–27 double-acting electric motors producing a total of 750PS for use while submerged. She had two shafts and two 1.23abbr=onNaNabbr=on propellers. The boat was capable of operating at depths of up to .
The submarine had a maximum surface speed of and a maximum submerged speed of . When submerged, the boat could operate for at ; when surfaced, she could travel at . U-1055 was fitted with five 53.30NaN0 torpedo tubes (four fitted at the bow and one at the stern), fourteen torpedoes, one 8.82NaN2 SK C/35 naval gun, (220 rounds), one 3.7cm (01.5inches) Flak M42 and two twin 2sp=usNaNsp=us C/30 anti-aircraft guns. The boat had a complement of between forty-four and sixty.
The boat's career began with training at 5th U-boat Flotilla on 8 April 1944, followed by active service on 1 December 1944 as part of the 11th Flotilla for the remainder of her service.
In two patrols she sank four merchant ships, for a total of .
On 6 April 1945 U-1055 was attacked by MTB-715 and MTB-719; apparently undamaged[1] U-1055 went missing on 23 April 1945 in the North Atlantic with no explanation after sending a message while en route to the English Channel. All hands were lost.[2] Other accounts (Flypast April 2021) state that U-1055 was sunk west of Brest shortly after 18:00 on 30 April by an anti-submarine PBY-5 Catalina commanded by Lt. F. G. Lake of 19 Group, but this attack actually resulted in the sinking of .
| Date | Ship Name | Nationality | Tonnage (GRT) | Fate[3] | |
|---|---|---|---|---|---|
| 9 January 1945 | Jonas Lie |  United States | 7,198 | Sunk | |
| 11 January 1945 | Roanoke | United States | 2,606 | Sunk | |
| 11 January 1945 | Normandy Coast |  United Kingdom | 1,428 | Sunk | |
| 15 January 1945 | Maja | United Kingdom | 8,181 | Sunk |