How deep can a stream really be?

This morning in church we did a song by Kutless called “All Who are Thirsty”.  The song is a beautiful, and does have an encouraging message, but it seem a bit off…. 

All who are thirsty… All who are weak… Come to the fountain… Dip your heart in the stream of life… Let the pain and the sorrow… be washed away… in the waves of His mercy… As deep cries out to deep

We have several water references here - The fountain becomes a stream that has waves (probably crashing because they are powerful enough to wash away), and then there’s the deep.  We could wax poetic on this all day, but recognizing the message, do the lyrics really support it or are they just cleverly assembled cliches?

So two questions - 

1) What does deep cries out to deep actually mean?  I’ve heard it in an Amy Grant or Gary Chapman song several years ago, and I didn’t know what it meant then?  Is that scripture or is that something that someone said one day, and then everyone ran with it, like Rufus.

2) How deep can a stream really be? and if it is deep, then how do two deeps call eachother? would it be considered long distance? 

MUST READ COMMENT STRING FOR THE RESULTS….