The swim attachment that I created doesn't work in Havok 4. Specifically, the character doesn't move forward when the arrow is pressed, and just animates in place. While investigating the problem, I noticed that there is a bug in llSetForce. You see, my swim attachment works by pushing a flying character around using llSetForce. However, the new bug is that llSetForce has no effect unless I am changing flying height while the force is first applied. In other words, I have to tap Page Up while holding down the arrow key to move. Note that I don't have to keep ascending while the force is applied, only briefly when first activating the force I am guessing this means the new physics don't recognize a character as an object that can be pushed around while the character is hovering, only while ascending or descending.