At first I thought it was some sort of switch, since it was hidden away at the end of passages (and we know that dead end passages ALL lead somewhere in games, unless it's meant to be a dead end where you get cornered), like the energy holding orb thingies.
So right before the nature boss, I swam along the bottom a little, saw the pod, and went "AH! Nature form must have something to do with these things!" (Since the game seems to love providing some way for you to practice your new abilities after you get new forms--the fight after the energy form, the tunnels after the fish form, the current that dumped you into the middle of a bunch of frogs after the beast form...)
