On 19 March 1943, the shooting began with a freighter identified as "Zogen Maru". A single torpedo hit broke the target in two; the aft end sank immediately, and the bow sank two minutes later. There were no survivors. Four hours later, "Wahoo" sighted another freighter, "Kowa Maru", and launched two torpedoes. The first hit under the target's foremast with a terrific blast, leaving a tremendous hole in her side, but the bow remained intact. The second torpedo hit amidships, but it was a dud and did not explode. Two more torpedoes were fired, but the freighter maneuvered to avoid them.