Booms near Winyah Bay

Last Sunday night through Thursday I was hearing constant noises coming from South winyah Bay.
I live near west side of Winyah Bay and the booms are definitely from the south.
About three to four a minute. Mostly late evening.
I’ve tried to look up Seismic surveying in area to no avail.
They sound like the big mortar shells you buy which shoot out of tube and explode but underwater.
Anyone know any info?