Jonah descended to one depth, viz. (Jonah 2:6) "The depth surrounded me," and they descended to two depths, viz. (Exodus 15:5) "The depths covered them." Jonah descended into one metzulah (whirlpool, viz. Jonah 2:4), and they descended into two, (Exodus, Ibid.) "metzuloth." And it is written (Nechemiah 9:11) "And their pursuers You cast into metzuloth, as a stone into raging waters."