But the wicked are like the tossing sea; for it cannot be quiet, and its waters toss up mire and dirt. (Isaiah 57:20)

[The ungodly are] wild waves of the sea, casting up the foam of their own shame; wandering stars, for whom the gloom of utter darkness has been reserved forever. (Jude 1:13)

The sea is an apt metaphor for the restlessness of the ungodly. They toss and turn, go to and fro, casting up muck and mire with ungodly thoughts and deeds. In Jude, he is speaking of infiltrating false teachers, but the metaphor is apt also to apply in general to the ungodly, their foaming spray prevents clear vision and in fact has no substance.

This episode is also available as a blog post: http://the-end-time.org/2021/04/16/the-sea-is-restless/

I use the NASB translation