Patrol 1

30 Dec 1941-13 Feb 1942

多摩川丸 Tamagawa Maru

Patrol 2

16 Mar 1942- 26 Apr 1942

No sinkings

Patrol 3

11 Jun 1942-2 Aug 1942

日山丸 Hiyama Maru

神陽丸 Shinyo Maru

函館丸 Hakodate Maru

Patrol 4

26 Aug 1942-20 Oct 1942

Patrol 5

22 Nov 1942-7 Jan 1943

Patrol 6

9 May 1943-21 Jun 1943

No sinkings

Patrol 7

18 Jul 1943- 30 Aug 1943

No sinkings

Note: Seadragon fired torpedoes at the abandonded hulk of 諏訪丸 Suwa Maru

Patrol 8

24 Sep 1943-5 Nov 1943

No sinkings

Patrol 9

14 Dec 1943-5 Feb 1944

No sinkings

Patrol 10

1 Apr 1944-25 May 1944

大寿丸 Daiju Maru - Note that JANAC confuses this ship with another of the same name, the 1279-ton Daiju Maru sunk March 18, 1944 by aircraft.

Unidentified trawler sunk by gunfire, estimated at 100 tons

Patrol 11

23 Sep 1944-8 Nov 1944

大天丸 Daiten Maru (listed as Taiten Maru in JANAC)

第一眞盛丸 Shinsei Maru No. 1

營口丸 Eiko Maru

Note: Seadragon is credited with sinking 黒龍丸 Kokuryu Maru in JANAC, but anaylsis of the events by Alden and others concludes that an earlier attack by USS Snook was the cause of Hokuryu Maru's sinking, and Seadragon's attack sank Shinsei Maru No. 1.

Patrol 12

3 Dec 1944-22 Jan 1945

11 ships, 44,900 tons, including one small vessel of an estimated 100 tons not credited to Seadragon in JANAC. Note that JANAC confuses Daiju Maru with a smaller ship of the same name, the 1279-ton Daiju Maru sunk March 18, 1944 by aircraft. Seadragon is credited with sinking 黒龍丸 Kokuryu Maru in JANAC, but anaylsis of the events by Alden and others concludes that an earlier attack by USS Snook was the cause of Hokuryu Maru's sinking, and Seadragon's attack sank Shinsei Maru No. 1.

JANAC - 10 ships, 43,450 tons. Note that the criteria JANAC used included all Japanese Naval vessels (although JANAC did not usually count warships less than 500 tons that were converted from merchant ships) and all Japanese merchant vessels of 500 or more gross tons known or believed to have been lost during the war. Differences between JANAC figures and current research are noted above.

Alden-McDonald credit Seadragon with 11 ships and 44,900 tons sunk.

SORG credits Seadragon with 15 ships and 77,200 tons sunk.

Japanese Naval and Merchant Ship Losses - JANAC on the NHHC website

JANAC on the Hyperwar website - https://www.ibiblio.org/hyperwar/Japan/IJN/JANAC-Losses/JANAC-Losses-6.html

SORG- http://archive.hnsa.org/doc/subreports-sorg.htm (Excel spreadsheet download)

Archives of the Pacific Fleet Submarine Museum (PFSM)

War Patrol Reports - USS Seadragon

Monthly Losses of Combatant and Non-Combatant Vessels

太平洋戦争時の喪失船舶明細表（汽船主体）- Lost Vessel table during the Pacific War (merchant vessels)

Alden, John D., and McDonald, Craig R. - U.S. & Allied Sub Successes in the Pacific & Far East during WWII - Fourth Edition, 2009

Cressman, Robert - The Official Chronology of the U.S. Navy in World War II, Naval Institute Press, 2000.

Wrecksite - https://www.wrecksite.eu/wrecksite.aspx

Miramar Ship Index - https://www.miramarshipindex.nz/

Imperial Japanese Navy Page - http://www.combinedfleet.com/

Wikipedia Japan - https://ja.wikipedia.org/wiki/

Japan Center for Asian Historical Records - National Archives of Japan - https://www.jacar.go.jp/index.html

Official U.S. Navy Photos - Naval History & Heritage Command

Japanese Merchant Ships Recognition Manual ONI 208-J on the maritime.org website.

Archives of the Pacific Fleet Submarine Museum (PFSM)

Japanese Merchant Ship photos - Wrecksite - copyright owners retain all rights. Photos used on this site will be taken down should the owner request their removal.

NavSource Online: Submarine Photo Archive