"The apostle calls them springs because they received the knowledge of our Lord Jesus Christ. Yet they are dry, or dried-up, springs, because they did not remain in union with Him" (Augustine). "He likens them to waterless springs because they lost the purity of preaching and the sweet water of life" (Theophylact).
In dry steppes there is an optical illusion. A thirsty traveler sees the likeness of water on the plain and takes it for a spring or a lake. He hastens toward it, but when he approaches, he is cruelly deceived, because it all turns into an empty apparition.
Clouds and mists driven by a storm. This is another likeness for such false teachers. Clouds and mists seem to promise fruitful rain. Yet, driven by a strong wind or storm, they disperse, and nothing comes from them.
So these false teachers, by their teaching, make the hearts of men barren for good works and for piety in general. They are hypocrites, having the appearance of piety but not its power (2 Tim 3:5).
Or the point of comparison may be this. Clouds and mists driven by the wind produce a storm and veil the sun, darkening it. So these false teachers trouble the quiet and peace of the soul, and by the darkness of error darken the pure face of the sun of righteousness.
Or again: "He compares them with clouds driven by the wind, meaning a contrary wind. For this reason he calls it a storm, since a storm brings what it drives into complete disorder. They are clouds, he says, not bright as the saints are, but dark and full of gloom" (Theophylact).
Driven is a word used of ships driven by a strong wind (Jas 3:4). In Luke's Gospel it is used of the possessed, whom the demon drives into the wilderness (Lk 8:29).
The gloom of darkness is an intensified expression. It means not only darkness or gloom, but dark gloom, or gloomy darkness. It is the strongest, or thickest, darkness and gloom. The darkness and gloom are both inward and outward (cf. note on v. 4; Mt 8:12; Mt 22:13; Mt 25:30).
Prepared, or kept, as for the fallen angels (v. 4), is the same word and expression. Eternal means unending, destined to continue unto all ages (Mt 25:41 and parallels).