UB-7 was a little over 28 metres (92 ft) in length and displaced between 127 and 141 tonnes (125 and 139 long tons), depending on whether surfaced or submerged.

Her fate is officially unknown, but sources report that may have struck a mine or been sunk by a Russian airplane.

[1][Note 2] UB-7 was part of the initial allotment of eight submarines—numbered UB-1 to UB-8—ordered on 15 October from Germaniawerft of Kiel, just shy of two months after planning for the class began.

Like all boats of the class, UB-7 was rated to a diving depth of 50 metres (160 ft), and could completely submerge in 33 seconds.

The process of shipping a UB I boat involved breaking the submarine down into what was essentially a knock down kit.

[15] So, upon completion of her leak repairs, the boat was commissioned into the German Imperial Navy as SM UB-7 on 6 May under the command of Oberleutnant zur See Wilhelm Werner,[4] a 26-year-old native of Apolda.

[4] Because of her limited range, UB-7 would not have been able to make the entire journey to Turkey, so on the night on 15/16 May, she was towed by the Austrian destroyer SMS Triglav through the Straits of Otranto and into the Ionian Sea.

[15][Note 6] By June,[16] UB-7 had reached Smyrna—not having any success on her journey there[17]—and joined U-21 and UB-8 in the Constantinople Flotilla (German: U-boote der Mittelmeer division in Konstantinopel).

[18] Once there, UB-7 was ineffective because she was hampered by her limited torpedo supply and her weak engines, which made negotiating the strong Dardanelles currents nearly impossible.

On 18 September, UB-7 torpedoed and sank the British steamer Patagonia about 10.5 nautical miles (19.4 km; 12.1 mi) from Odessa.

[22] Because Bulgaria had joined the Central Powers, battleships of the Russian Black Sea Fleet, and aircraft from the seaplane carriers Almaz and Imperator Nikolai I began attacks on Varna and the Bulgarian coast on 25 October.

[1] Bulgarian sailors practiced in the pair of boats and technicians were sent to Kiel for training at the German submarine school there.

With the submarine out of the way, Rear Admiral Aleksandr Kolchak sortied with dreadnought Imperatritsa Mariya, cruiser Kagul, and five destroyers.

[5][30] Authors Dwight Messimer and Robert Grant are each dubious of this claim,[30][32] and the fate of UB-7 is still officially unknown.