Based on the Coast Guard Historian’s timeline, https://www.history.uscg.mil/research/chronology/
With inspiration from Mike Kelso

February 21

USCGC Spencer (WPG-36) in 1942 or 1943. Spencer sank U-175 with assistance of USCGC Duane, on April 17, 1943.

1943  CGC Spencer received credit from the U.S. Navy for attacking and sinking the U-225 in the North Atlantic.  The British Ministry of Defence has since recorded that the U-225 was actually destroyed by B-24 Liberator “S” of RAF No. 120 Squadron on February 15, 1943 and they have revised the official British records to reflect this change.  However, the renowned German naval historian, Professor-Dr. Jurgen Rohwer, stated that Spencer “probably” attacked and sank the U-529 instead, although the Spencer has not received official credit for that sinking.

2008  On February 20, 2008, two U.S. Air Force F-15C fighter jets from Eglin Air Force Base, Florida, collided over the Gulf of Mexico off Panama City.  Coast Guard HC-144A, No. 2303, and its crew, which were diverted to the scene from a routine training flight.  They located the first pilot and directed his recovery.  Both F-15C pilots were eventually recovered; regrettably only one was recovered alive.  This search & rescue (SAR) mission included two important “firsts” for the U.S. Coast Guard’s new HC-144A Ocean Sentry Maritime Patrol Aircraft.  For the HC-144A, the incident marked its first SAR mission, and its first use as an On-Scene Coordinator (OSC) platform.