I too got the raft stuck, once, by getting off, and then missing when I was getting back on, falling in the water, and respawning on the other side of the water >_<
Getting past the medallion sylph is possible! Here's how:
First, make it visible. Yeah.
Next, wait until it's gone all the way to the left. When it starts to move right, follow it until the first alcove. Get in quick!
Then, shortly, it'll come back left. As soon as it passes you going left, go down and run as fast as you can to the second alcove.
If you made it in time, then the sylph'll just miss you. Then, it's a simple matter of waiting for it to pass left again to make the last leg of the journey.
I was stuck for getting the key, until I read ShadowTiger's spoiler. I must go try that now!
Edit: Works like a charm! I then got the bomb, got into the next area, learned of the secret shortcut (>_<), and then promptly got killed
Edit again: I guess there's nothing more after you get your swo... er, stick back.