Well, image_angle works nicely for this, so I am probably going to keep it.
Also, I'm currently re-working the collisions. They work nicely, 'cept for monitors and springs, but I did make some changes for them. Also, I finished DSP effects, so the bg music and sound effects sound slightly different when underwater.
EDIT: I finished the monitors and springs, and I am satisfied. I fixed a few bugs with the monitors (eg. you were a few pixels above, you were able to break a box when going slowly on the edge), and springs are less buggy than they were. (the you are a few pixels above bug was fixed, along with another bug that I create after demo 3).