Outside the United States, his pick is Cabo Pulmo, on the tip of Baja California. You can pack it up and it'll hold its shape. That requires a good mix of grain size without getting too large a grain. Color also is important for contrast when you are carving windows in your sand castle, he said. If it's a lighter colored sand, you get a nice contrast.
Seal Beach is dark sand but when it dries out it's light enough to make really good contrast.
Nautical nuts can go crazy,too.