I visited a small beach in Long Island once, a garden variety one except less crowded and with pebbles in the sand. The beach was half a mile long, occupied by maybe two hundred people. Most were sunbathers but there were also many families with kids playing in the sand. One particuar family of 6 had a giant tent. We were there at 4PM so the sun shone less power UV rays, fortunate for us, unfortunate for the sunbathers. I decided grab the proper tools and construct a mini sand fortress that could withstand the waves. After several failed attempts I finally made a fortress large enough and built quick enough to be built before a big wave destroyed it. Fortress is an exaggeration, it was just several reinforced walls made with an ideal sand to water ratio. Some young children were watching my "fortess" in awe, made sense because their little sand castles paled in comparison to my design. I would bet you a hundred dollars that one of them took over my wavebreaker after I left, it's a practice commonly used on beaches. Once at a crowded beach I made a absolutley MAMMOTH series of walls and pits, after withstanding waves became too easy I built a castle behind it. It took 4 hours total. A few others started copying me so I spoke to a kid building a rather large castle near mine so we agreed to construct a wall or two connecting the two complexes. Then I had to leave so I gave it to him.