Verses with the word sink in the Old Testament (3 verses):

Psalms 69:2
I sink in deep mire, where there is no standing: I am come into deep waters, where the floods overflow me.

Psalms 69:14
Deliver me out of the mire, and let me not sink: let me be delivered from them that hate me, and out of the deep waters.

Jeremiah 51:64
And thou shalt say, Thus shall Babylon sink, and shall not rise from the evil that I will bring upon her: and they shall be weary. Thus far are the words of Jeremiah.