system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: What makes the patterns on the surface of water? Eg. the ripples in one part and complete stillness in another? Is it just the wind or is there more to it?
gpt
There's a *little* more to it. Ripples are initially created by a disturbance of the surface, whether it's wind, a fish, a bird... etc. The ripples move outwards in concentric rings from the point of the disturbance.

Where it gets interesting is when those ripples collide with something. That can be the edge of the lake, a reed, various other static objects, or other ripples. 

When they encounter static objects, ripples behave differently depending on the angle that they strike. They can either be reflected (bounced) back, they can be distorted around the object, or they can be absorbed. This can change the "intensity" (amplitude) of the ripples, and change their direction.

When ripples hit other ripples, several things can happen. If they are the same amplitude, and happen to collide at the right time, they will cancel each other out, and this results in a patch of perfectly still water.

If they collide at the "wrong" time, they can enhance each other. This results in an increase in intensity (amplitude), and the ripples get bigger. However, they will move slower, as the energy is "changed" from movement into amplitude. So you get a patch of very disturbed water.

Look into how electromagnetic waves behave when they interact with each other - ripples work in pretty much the same way.