Since there are no German records about O 13 having been sunk it is assumed that the submarine ran into a mine, a distinct possibility since O 13 was patrolling in an area known to have been mined,[7] possibly the same minefield where the Polish submarine ORP Orzeł was lost. One other possibility is that O 13 was rammed by the Polish submarine ORP Wilk, which reported running into an unidentified submarine on 20 June at 0.25 am, but that submarine allegedly had a deck gun mounted forward of the conning tower and O-13 did not.[8] Moreover, the newest analysis of the Wilk's damages shows the most probable possibility: that it collided with a German minefield protector buoy, rather than a submarine.[9] Searching of the O13 wreck in the area of the Wilk's reported collision was fruitless.[9]
Monument and memory
In September 2009, Dundee International Submarine Memorial was dedicated to the memory of the 296 sailors and commandos who served on submarines operating from there and who did not return, among them the crews of O 13 and O 22.[10]O 22 was located near Norway in 1993.[11]O 13 is referred to as "still on patrol", as it is the last Dutch submarine still to be found, of the seven submarines the Royal Dutch Navy lost in World War II.[12] In September 2012, the Royal Netherlands Navy announced they would renew the search with new, advanced equipment.[13][14]