A postwar German study concluded that UB-3 was likely the victim of an unexplained technical problem in the absence of any minefields or enemy action.

[6][Note 2] UB-3 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-3 was rated to a diving depth of 50 metres (160 ft), and could completely submerge in 33 seconds.

[10][12] Because of her limited range, UB-3 was towed by the light cruiser SMS Novara of the Austro-Hungarian Navy[13] through the Straits of Otranto and cast off near the island of Kérkira.

UB-3's planned route was south of the Ionian Islands, around the Peloponnese, through the Cyclades, north around Khios and Karaburun, and into the Gulf of İzmir.

The Germans received a garbled radio message from UB-3 when she was about 80 nautical miles (150 km; 92 mi) from İzmir, but were unable to completely understand it.

[5] A postwar German study concluded that UB-3's loss was probably the result of some unexplained technical problem, because there were no minefields along UB-3's route and no record of any attacks against U-boats in the area.

[10] British records, and some sources based on them,[14] give the particulars of UB-3's demise as being in the North Sea on 24 April 1916, which authors R. H. Gibson and Maurice Prendergast assert was actually the fate of UB-13.