"premature explosion of two torpedoes"

SAT 18 SEP 1943
Pacific
TF 15 (Rear Admiral Charles A. Pownall) aircraft [attack] Tarawa, Makin, and Abemama, Gilberts, to decrease Japanese pressure on the Ellice Islands and provide operational training. During the attack on Tarawa, TBFs, SBDs, and F6Fs from carrier Lexington (CV-16), and small carriers Princeton (CVL 23) and Belleau Wood (CVL 24) sink Japanese motor torpedo boats Gyoraitei and Gyoraitei No. 3. [Three carriers to sink two P.T. boats? Mmmm ...]

Submarine S-42 (SS-153) damages Japanese gunboat Chowa Maru, 50°22'N, 155°43'E.

Submarine Scamp (SS-277) attacks Japanese convoy north of New Guinea, sinking army cargo ship Kansai Maru 00°41'N, 146°28'E, but although damaged by depth charges (perhaps dropped by submarine chasers Ch 38 and/or Ch 16, known to be among the escorts) remains on patrol.

Submarine Spearfish (SS-190) damages Japanese torpedo boat Sagi (premature explosion of two torpedoes), 29°08'N, 134°29'E.

Submarine Trigger (SS-237) sinks Japanese merchant cargo ship Yowa Maru, 27°20'N, 126°53'E.

Atlantic
U.S. freighter William Pepperell is attacked by German submarine U-260, 55°02'N, 29°27'E, but the torpedo detonates in the ship's torpedo streamer, causing only minor damage to the freighter herself;
there are no casualties to either the 42-man merchant complement or the 26-man Armed Guard (see 20 September 1943).