The O-20 was a Dutch O-19 class submarine in the Royal Netherlands Navy that saw service during World War II. O-20 along with her sister ship O-19 were the first boats in the world to be equipped with a "getrimd diesel systeem" or "snort system" that allowed the submarine to run its diesel engines while submerged.
O-20 was laid down June 15 1936 as the K XX. After which at some point she was renamed O-20. She was launched on January 31 1939, and on August 28 of the same year she was commissioned and assigned to the command of Ltz. I A.J. Bussemaker.
By December 23 1939 O-20 reached the Netherlands West Indies via the Panama Canal.
Given a new patrol route, O-20 spotted Japanese destroyers off and on from December 17 to 19th. On the 19th at 7:00, she spied two Japanese transports being escorted by two destroyers. In a few hours a third destroyer joined them. These destroyers were the Ayanami, the Uranami, and the Yugiri.
The destroyers scanned the bay for O-20, dropping eight depth charges every half hour. Some of these detonated directly above the submarine, but were set to detonate too shallow to badly damage it. (It turned out that the next deepest setting would have buried the charges in the mud)
That night, the commander attempted to surface to escape at full speed, but was detected by a new Japanese sonar. Two more tanks were blown and the sub surfaced at a 25° angle and engines were set to full speed. Because of some pre-existing defects O-20 began to take on water at the screw shafts.
The hatch was opened and with no enemy ships in sight, the machine guns were not manned or prepared. The commander decided to dump a fuel tank in order to escape even faster, which rose the sub even higher in the water exposing the diesel exhaust pipes. Due to more pre-existing damage coupled with damage from the depth charges, the pipes began to spark, giving away the O-20's position to anyone who looked in her direction. The commander decided to do nothing.
After daylight, Uranami rescued the 32 survivors, she had dropped depth charges throughout the remainder of the night to keep sharks away. Seven men, including the commander were found to be missing. The commander was known to not have been wearing his life vest, it is possible that this is how the other six perished as well. An alternative suggestion is that since the six men all worked in the engine room, they may have not been warned in time to evacuate the ship before it was scuttled.
The wreck is located approximately NE of Kota Baru, Malaysia at a depth of about 144 ft (44 m). The divers report that the masts are no longer visible, the snort is gone, and that the bridge was shelled so badly it could be seen through easily. The divers retrieved a deck phone from the sub in order to positively identify it, but left the wreck alone, as it was likely the gravesite of six seamen.