2 Peter 2:17
The word of truth is the water of life. In which, it refreshes the souls that receive it. But those who deceive (false prophets/teachers) speak error because there is no truth in them. As clouds hinder the light of the sun, so do the false prophets darken counsel with words that have no truth. Being that these men promote darkness in the world, it is fitting that the mist of darkness will be their place in the hereafter. They gave off an impression of being wellsprings however they had no substance. This would suggest how they were as instructors, wellsprings of water in the desert but without water. Darkness is an example of God's judgment.
Peter is warning of false prophets coming into the church. This is a danger to growing Christians. A well without water is a dry well. There is no nourishment for life. It's pointless. Drawing dirty water from a dirty well is just as bad, there is no nourishment. If there is no water, then there is no life.
When a well dries up it is filled in because the dry well is a danger to others. A well that is stagnant if not tended to and used becomes unhealthy.
Wells are often supplied by springs & rain - Proverbs 16:22, Psalms 84:6.
They are often deep and too difficult to draw from - John 4:11.
They are also covered to prevent being filled in - Genesis 29:2,3.
Some wells were stopped up by the enemy - Genesis 26:15,18; 2 Kings 3:19,25.
Occasionally, some wells didn't have water - Jeremiah 14:3; Zechariah 9:11.
A Sinner is a desert soul, barren, with no water.
A Backslider has dirty water or is slowly drying up.
For comparison, we could look at the differences between the physical and spiritual of being with or without water. What can you think would fit these columns?
A well or body with water A well or body without water