From: Dictionary of American Naval Fighting Ships, Vol.VII - p 135
A sea nymph of Greek Mythology. She was the daughter of the sea god Nereus and the mother of the Trojan War hero Achilles.
The third Thetis--a twin-screw, diesel-powered, steel-hulled Coast Guard patrol boat--was laid down on 9 May 1931 at Bath, Maine, by the Bath Iron Works Corp. ; launched on 9 November 1931 ; and delivered to the Coast Guard on 27 November 1931 ; and was accepted for service two days later.
Assigned to Division 2, Destroyer Force, on 30 November, Thetis departed Bath on 1 December for shakedown training off the eastern seaboard. During this cruise, she visited Washington, D.C. Subsequently transferred to the Special Patrol Force of the New York Division, the ship was stationed initially at Stapleton, NY.
By 1934, the vessel had apparently been transferred to Boston, Mass. She remained on duty there through July of 1940. Mid-1941 found Thetis shifted south to Key West. As one of the six ships of her class taken over by the Navy, Thetis was assigned to the East Coast Sound School, Key West, Fla., on 1 July 1941, concurrently with the establishment of the four Sea Frontiers. By late 1941, the Coast Guard patrol boat was assigned collateral duties in the Gulf Patrol, a unit of Task Force 6. Other ships in this group included Destroyer Division 66, Subchaser Division 31 (less PC--451), and three of Thetis' sister ships.
Attached to the Sound School at the time of the Japanese attack on Pearl Harbor on 7 December 1941, Thetis was classified WPC--115 sometime in or around February of 1942. At about this time, early 1942, German U-boats experienced what they considered a "happy time" off the eastern seaboard, as American vessels were not yet being escorted from place to place. American antisubmarine measures were largely crude and ineffective for nearly the first four or five months of World War II.
On 9 June, while in the course of carrying out her normal training and patrol missions off the east coast of Florida, Thetis took part in an unsuccessful search for what was suspected to be a U-boat. However, the torpedoing of the American freighter Hagan on the evening of 10 June 1942 gave the American "hunter killer" forces something unquestionably real to hunt for. She was U--157, and Hagan had been her first victim, being damaged but not sunk by the U-boat.
Accordingly, a "dragnet" was thrown out to find and destroy the submarine before she could attack any other ships. This intensive search effort involved radar-equipped Army B--18 bombers, three destroyers, several PC's, and Thetis' sister ship, Triton (WPC--116). On 13 June, Thetis picked up a definite contact and plunged ahead for the kill. With the unseen target 200 yards two points on the port bow, Thetis went to general quarters and continued ahead about 1,000 yards before turning to port and increasing to full power. Regaining contact upon steadying out on her base course--she had temporarily lost it while maneuvering --Thetis bore down on the U-boat.
The patrol craft dropped her first depth charges at 1558--5 charges set for 200 to 300 feet at five-second intervals. She also launched a further two from the ship's "Y" gun at the time of release of the third charge. After making the run and observing the explosions, Thetis turned to starboard to observe the results of her attack, and observed a "water slug" (a disturbance in the water) a short distance to the right of her own wake. As the commanding officer of Thetis observed, the "slug" did not resemble the disturbance usually associated with the explosion of depth charges.
Thetis observed pieces of freshly broken wood float to the surface at 1618, as well as articles of clothing. Thetis then maneuvered into the flotsam and jetsam and retrieved two pairs of leather submariner's pants of the type usually worn by U-boaters in the northern latitudes.
PE--27 soon made an approach and dropped a marker buoy. Thetis, meanwhile, sighted and picked up a tube of lubricant made in Dusseldorf, Germany. While Thetis returned to rearm at Key West, PE--27, PC--519, and Triton all carried out attacks--all in actuality unnecessary as Thetis had already sunk the U-boat on her first run. Thetis came back and conducted one more attack, but U--157 had already gone to the bottom, entombing her crew in her hull.
Thetis remained with the Navy's East Coast Sound School for the remainder of the war, conducting coast-wise convoy escort, sonar training, and antisubmarine patrols for the duration of hostilities. Returned to Coast Guard jurisdiction after World War II and serving into the early 1960's, her name was removed from Coast Guard lists at that time.