It's summer, which for some means spare time at the beach, splashing in the waves and...building sandcastles. On today's episode, Emily Kwong asks: Scientifically, what is the best way to make a sandcastle? What's the right mix of water and sand to create grand staircases and towers? Sedimentologist Matthew Bennett shares his research — and personal — insights. Happy building! Wondering what science and engineering are behind other summertime activities? Or just want to share your greatest sandcastle creations? Shoot us an email at shortwave@npr.org.