Select and install a pendant light fixture in a style compatible with the room's decor. It must have light bulbs that cast light downward to illuminate the cascade of shells below. It must have one or more lampshades arranged to shield the light source and a sturdy metal framework from which to suspend shells.
Purchase pre-drilled white or natural abalone shells in the shape desired from a bead shop or from Internet sources. Shells come in a variety of shapes, including flat discs, ovals and hearts.
String the abalone beads or pieces on the fishing line, knotting between each piece at intervals as desired. Create a cascade or waterfall effect by varying the length of the strands. Secure each strand to the framework inside the lampshade by tying square knots and securing the knot with clear glue.