FIGURATIVE MEANING OF THE PROVERB
In life While making decision, you should think carefully. Don't be rash and hasty. Careful thoughts will enable you to look at both sides of a coin critically, weigh them on an imaginary scale, and determain the one that outweighs the other.
The river, here, could be your enemy or your challenges. While Your feet are your weapon that you can use to defeat your enemies. Furthermore, putting both legs in the river is a fool action. This may gives your enemies the opportunity to ensnare and take your life slowly without hestating. Thus such rash action is sheer foolishness on your part.
Therefore, when you put one feet in the river, you are just trying to see how violent and strong your enemy is.
If the river is deep, then, you don't put both feet: you device another means to defeat your enemies.
This is called WISDOM
THINK TWICE.
BE WISE.