Jamieson, Fausset and Brown on Jonah 2:6

6. bottoms of ... mountains--their extremities where they terminate in the hidden depths of the sea. Compare Psa 18:7, "the foundations of the hills" (Psa 18:15).

earth with her bars was about me--Earth, the land of the living, is (not "was") shut against me.

for ever--so far as any effort of mine can deliver me.

yet hast thou brought up my life from corruption--rather, "Thou bringest ... from the pit" [Maurer]. As in the previous clauses he expresses the hopelessness of his state, so in this, his sure hope of deliverance through Jehovah's infinite resources. "Against hope he believes in hope," and speaks as if the deliverance were actually being accomplished. Hezekiah seems to have incorporated Jonah's very words in his prayer (Is 38:17), just as Jonah appropriated the language of the Psalms.