During the invasion in Normandy the US Coast Guard had a major role. Not only were many of the landing craft operated by Coast Guard Coxswains (many of them had lots of experience operating small boats in the surf); also they operated 60 wooden hulled patrol boats near shore rescuing survivors from sunken boats. The also had Beachmasters (both Navy and Coast Guard) directing boats and LSTs where to land.
Here's a link of of 5 facts about the Coast Guard on D-Day:
https://coastguard.dodlive.mil/2014/...d-at-normandy/
Here's a little "use your imagination" collage I put together a few years ago as a reminder the Coast Guard did operate ships and small boats in WWII. The Garand is a short barreled "TANKER" that never was produced by the US Armory at Springfield, MA although several prototypes were built and some were built in Theater in the

ippines. Mine was assembled from a kit that Numrich used to sell.