Can anyone explain how to procedurally generate lake floor(sand) texture like on screenshot below?

You mean the texture that's completely covered up by the water? ?

2 minutes ago, fleabay said:

You mean the texture that's completely covered up by the water? ?

Yes

23 hours ago, Fatigue said:

Yes

I really hate to ask but

Why? It's killing me.

9 minutes ago, fleabay said:

I really hate to ask but

Why? It's killing me.

There was a little misunderstanding.

I meant diffuse texture which imitates a relief under water.

You could use the distance from the shore. When near the shore, use more sand (and less water) in the texture. When further from the shore, use less sand. At some distance stop using sand and you have "deep water".