Test the sand. Squeeze wet sand and roll it back and forth in your hand. If it stays together, it’s good sand. If it falls apart, “you’re in the wrong spot—or on the wrong beach,” says Vander Pluym.
Build a base. Make a circular wall out of dry sand, 6 inches high and 3 feet wide. Add 2 inches of water to circle, then 2 inches of sand. Tamp until water drains. Add dry sand to wall and repeat layering, angling inward to form 18-inch mound.
Construct towers. Place a bucket, with the bottom cut out, handle side down on the mound. Alternate layers of sand and water in the bucket, 2 inches at a time, tamping as you go, finishing with water.
Perform lift-off. Have one person tap the bucket to release sand right before another one lifts it straight up. Repeat process for more towers, and remove loose sand from around the mound.
Add details. Use an offset spatula to square off towers and make stairs; a funnel for roofs; a melon baller for corbels; and a disposable knife for arrow slits—“a neat little detail that makes a castle look like a castle.”
Vander Pluym’s Redondo Beach–based company, Sand Sculptors International, offers lessons and a how-to DVD, Sandcastles for Everyone; sandsculptors.com