A crochet shell pattern or shell stitch is a pattern that looks like interlocking scallop-shaped seashells. The shells can form a closed pattern or an one with openings between or within the shells.
There are a number of methods for creating shell patterns, but each shell pattern typically starts with a row of chain stitches. To make one shell pattern, the crafter double crochets in the third stitch from the hook, then makes four more double crochets in the same stitch, skips three stitches and repeats the series of double crochets in the next stitch. Repeating this sequence creates a row of shells.