Fill the conch shell with sphagnum moss that has been dampened with water. This particular shell is large and has a deep natural pocket. Pack the moss snugly inside the pocket and allow some of it to trail over the rounded side of the shell.
Place a tall clump of decorative grass near the lowest end of your shell. Push the pencil into the moss and then insert the ends of the grass. Tamp the moss around the base of the grass so that it is secure.
Cut three stems of phalaenopsis orchids in varied sizes. The tallest stem should be about eight inches high. Insert a pencil into the moss to create three deep holes. Position them close together. Push the ends of the stems into the holes. Tamp the moss around the stems until they stand upright and are secure.
Position a rectangular mirror in the center of your table. Set your conch shell in the middle of it.
Fill four low, clear glass small bowls 1/4 of the way full with small shells. Add water and float a single candle in each bowl. Arrange the bowls around the conch shell on top of your mirror.
Scatter pieces of beach glass among the candles. Allow some glass pebbles to tumble over the edges of the mirror and onto the tablecloth.
Cut several orchid blossoms from their stems. Place them randomly among the pieces of beach glass. The blossoms will remain fresh for several hours.