The sarong skirt is definitely one of the trends of the moment.
This type of skirt is basically any fabric that wraps around the waist, which can be used as beach wear, as a bikini or as a dress, skirt or other garment.
So if you're thinking about those pieces you tie on after you get out of the sea, you're not wrong...just imagine them a little more refined. Here are some models:

River Island Yellow Print Wrap Sarong Midi Skirt

Banana Republic Linen-Blend Tulip Midi Skirt

Eloquii Twist Detail Sarong Midi Skirt

Milly Knotted Sarong Skirt

Stradivarius Satin Jacquard Knot Wrap Midi Skirt

Mango Linen-Blend Wrap Skirt

Diarrablu Seur Atoll Print Wrap Skirt

& Other Stories & Other Stories Lace Cover-Up Sarong

Donna Karen Rustic Chic Geometric Sarong Skirt

Stella Jean Printed Silk Wrap Pareo Skirt