Balance skill and naval warfare


Please, can anybody confirm me whether you have to pass balance skill checks EVERY combat round when fighting on a ship?

At first, I thought it would give a pirate-class character a nice edge during any battle at the sea, since a pirate can easily purchase the 5 ranks needed in order to avoid being flat-footed when you use your balance skill.

This would reflect the advantage a sea wolf would have over an unbalanced, clumsy land fighter -who has better Base Attack Bonus and fighing feats but is not so suited to sea-based combat- when fighting on his carrack.

However, some notorious NPCs from Pirate Isles don't even have the skill. Does it mean the skill is not used that way? Was this done on purpouse?

Any comments are welcome.
The only thing close I belive is Up The Rigging, a new feat that eliminates that character's need to make a Balance check during a Boarding Action. As far as I can see, you otherwise don't need to make Balance checks during shipboard combat unless maybe you're crazy enough to be up in the rigging or n a mast a-la Erol Flynn or something. ;)