Groins, as used here, refers to large rock erosion controlling berms built at right angles to the beach and extending out a considerable distance into the ocean. Along Folly Beach they are found about every few hundreds of yards and are frequently mostly covered with water, making them more than a little dangerous if you ride a wave onto them unexpectedly. They are generally considered to be counterproductive to the retention of sand (their original purpose), creating additional turbulence and causing more erosion. They've been up and down the length of my 5 mile barrier island for as long as I remember. A recent sand renourishment project has them mostly covered with sand at present. I'll post a picture at some point...