Ooh, something I actually know about. I did my bachelors capstone on the role of the USCG in the Atlantic during WWII until the end of the Battle of the Atlantic.

They were involved in several areas:

• Search and rescue (including assisting other vessels sunk during convoy operations).
• ASW, many USCG vessels were smaller destroyers or patrol boats.
• Guard the coast, literally. There was a beach patrol. They were a part in stopping Operation Pastorious from succeeding.
• As small boat experts, help pilot landing craft and train the Navy and Army pilots of those vessels.
• There were also members of the newly formed civilian Auxiliary who were given status as temporary Reservists and armed with old weapons and used their personal vessels as coastal anti-sub pickets/

Only one member of the USCG received the medal of honor, Douglas Munro who was killed during an evacuation of Marines from Guadalcanal. If a Marine ever rips on a Coastie, they can easily remind them that Chesty Puller was saved by Munro.

I am going to see if I can find that paper for you.

They also took part in all amphibious assaults carried by US forces in both Europe and the Pacific. Many of the sailors and officers manning the landing crafts were in fact USCG personnel, Other tasks included weather monitoring and navigational aids and as cited in other post search and rescue which included planes and not just vessels. Following the British model they would have planes equipped with detachable boats in their bellys to be dropped near the downed pilots, B-17 were used and by the end of the war few B-29 came into that rol too.

If you you are a man of details I may suggest you check the original source, the USCG historical office has digitalized many of its documents and involvement in WW2, a wealth of history there. Check this link:

https://www.uscg.mil/history/WW2Index.asp

Edited for minor details and typos.