'Seehund' (ii) was a German naval minelaying operation in the Kara Sea by Oberleutnant Walter Wichmann’s U-639 (17/28 August 1943).

After laying 24 TMB mines in the estuary of the Ob river on 21 August, the U-boat was sunk by torpedoes from the Soviet submarine S-101 with the loss of all 47 of its crew.