This question has been bothering me ever since I watched the ending of the fourth episode of season 7 (The Spoils of War).
Jaime charges towards Daenerys and Drogon. He is charging along the bank of a river; so, it seems that the water is obviously not that deep (maybe ~0.1 Jaime Lannister). Now, someone hurls him from his horse and they fall into the water, and suddenly, the river seems deeper than seven Jaime Lannisters (see below screenshot).
The point at which he falls isn't that far from where the horse was riding along the bank. So my question is - do real rivers behave like this? That kind of gradient seems scary if it can be real. And if so, does anyone know of any particular rivers that might do this?