Personally I didn't use dual form almost at all in the gauntlet, really, imo if you want to get through the gauntlet the easy way nature form is best.
1) At the beginning of the gauntlet just swim along near the walls. If things chase you/shoot at you drop a thorn behind yourself.
2) This makes the whole room of nautiluses (is that even how it's pluralized?) a complete non-challenge. Just get near a wall, put thorns on either side of yourself and wait.
3) I personally just swam through the final room without bothering to fight, so I'm not sure if the thorns tactic will work there.
Nature form + narrow passageway = victory
