Why does it say "Yordei ha'Yam ba'Aniyos"? Does one descend to the sea?
Radak: Even though the sea is higher than the land, the shore is higher than the sea.
Radak citing his father: Boats are deep; one descends into a boat - "va'Yimtza Aniyah... va'Yered Bah" (Yonah 1:3).
Why are seafarers discussed last?
Malbim: This discusses after they return from their exile, and returned on the sea in ships, Hashem showed His wonders another time, so they will praise Him when they come to their land.
What Melachah do they do in the sea?
Radak: They work with the pole, mast, ropes, oars and other Kelim needed for the ship. Where the water is deep, more work is needed.
Malbim: They know strategies to maintain a ship at a time of a storm, and be saved.
Why do some texts have backwards Nunim before and after this and the next four verses?
Rashi (17, based on Rosh Hashanah 17b): There are special Simanim 1 in this Mizmor; they are exclusions. Crying [to Hashem] helps only before the decree, but not after the decree.
Some texts of Rashi say the Reishim in "ba'Tzar" (i.e. in verses 6, 13, 19 and 28) are backwards; some say that there are backwards Nunim (between verses). In some editions of Rosh Hashanah, a diagram in Rashi shows backwards Nunim, and so say the Aruch and Ritva there. Maharsha - the Beraisa taught this regarding seafarers, for they are considered individuals. The above cases are unlike individuals, and screaming helps even after a decree. Chashukei Chemed (17ab) - they are like individuals, for each prays about his own affliction, but not for his colleague (Parshas Derachim, Drush 13). This is because they are strangers who do not know each other (Shem mi'Shmuel Shavu'os p.89, citing Avnei Nezer).
