You are supposed to walljump that bit in the Sun Temple, or, at least, that's the only way I've ever gotten there. As for the wall and the tongue, you're missing something. You're not looking for another form, but swim around in both parts of the veil some more. If you look around near the surface, you'll find something interesting.
To be more direct: SPOILERS (copy and paste into something to read):
You're looking for another person. Swim around in the upper part of the western (I think) map of the veil until you see a blue guy in a helmet, then follow him.If I'm completely misunderstanding where you are, then sorry, and I'll let someone who's played more recently answer your questions.
