I bought 10,000 shade balls and tried to swim in them. They appear to act like a non-Newtonian fluid: rigid under high shear stress, but they flow like a liquid under low shear. My sense was that swimming in shade balls would be difficult but still doable. This was roughly true for the single layer of shade balls. The shade balls slide past each other so they act like a liquid, albeit a viscous one owing to their significant inertia. It's much more intense exercise and it's also annoying to be bombarded with shade balls on all sides of your body, particularly your head. With multi-layer shade balls (as exists on much of LA reservoir) things get significantly more difficult. The balls bunch together and when you try to move through them quickly, they become more rigid, providing significant resistance to motion. This has the benefit that you can lie on them and as long as they stay trapped under you, you can float on them. But a little bit of motion causes them to move around and you sink through quickly.