It's one thing to know how to knot a rope, it's another to do it highly effectively. I'd say it's something you could do untrained, but I'd let someone with ranks in Escape Artist (since knowing how to reverse engineer bonds is really helpful for getting out of them), Profession (Sailor) and/or Survival count their ranks toward the DC of escaping the bonds.
As far as skill discussions, I'm kind of annoyed at Jumping being a part of Acrobatics, I believe it's largely a function of ones strength- I've consolidated Swimming, Climbing and Jumping into Athletics, which I obviously lifted from 4th Ed. I figured I'm not hurting anyone by giving Joe Fighter with 2 skill points to spend per level a little less to spread those scant points across.
