Swimming and Holding your breath...

[The Arcanist]

bear with me for a second please, let me explain the situation...

im writing this adventure for my group in which they'll be trapped in the ethereal, within a haunted house, lots of ghosts and all and i dont need to give them magic weapons, hehehe, yes, im a cruel DM...

now the grand finale and climax of the adventure would be within a sunken ship by a dock next to the house, there within a pocket of air they return to the material plane, at a depth that at the moment is ranging between 200 to 400 feet, and they'll need to swim back up... yes im evil... cant wait to see the face of the full-plate clad paladin...

now, in most places around the core rules it says you may hold your breath 2 rounds per point of constitution before risking suffocation, which starts at DC 10.

yet on the description of the swimming skill it says you can hold your breath only one round per point of constitution, a round costs double if you take standard or full-round actions.

furthermore, on the skill's description it mentions that with the corresponding DC you might move 1/4 your speed as a move action or 1/2 your speed as a full-round.

who in their right mind would take it as a full round action is beyond my understanding as it will consume extra-air while you could take two move actions, advance the same ammout and still be within the only move actions restriction...

so my questions would be something like:

1: how many 'free' rounds afterall? 1 or 2 per point of constitution? (im assuming 1 at the moment)

and...

2: should i allow two move actions? seems kinda contradictory to the full-round action note on the skill. or is that perhaps only for swimming on the surface to reduce the number of rolls by half?

ps. if anyone's interested in the adventure just let me know and when its done i'll be glad to share it with anyone interested.