Water Striders. Filmed in slow-motion, of course.

There’s actually a bit of physics here, starting with the obvious, the reason they don’t sink: surface tension. Water is polar, so the molecules tend to attract each other, making the surface act like a series of springs and able to support small masses, up to the point that the attraction is overpowered.

Once the strider starts moving, we can see some more physics in action:

The water strider is actually hard to see in this picture — it’s a little above and the the left of center. The black dots are a shadow of sorts. The insect would not cast much of a visible shadow if it were on a flat surface; it’s small and light will tend to diffract around the legs. But what’s happening here is that the feet make an indentation in the water and it turns the now-curved surface of the water into a lens. And the lens is concave, so the light diverges and leaves a dark spot because light has been directed away.

The water strider has been moving, and this disturbs the water. We see the waves from this disturbance and the interference as two separate waves pass through each other.

Once again, you’re seeing the effects displayed on the creek bed, rather than the surface.