
Gronk de'Morcaine |

Actually I already have a masterwork underwater crossbow. Since I was already paying for a masterwork, I decided the miniscule cost for 'underwater' was a good insurance.
I will get a spear, since I'm not sure a GM will let me swing the Morningstar without penalty.
I can't now find the swim fins or air crystals, but I know I've seen them before. Anyone know which book has them?
Potion Sponge is an Undine item. I don't think PFS lets me use racial equipment, but I'm not sure. I will have to check into it.
Potion of Water Breathing is a bit pricey, but I will get at least 1.
Potion of Touch of the Sea and/or Air Bubble will only last a minute (PFS minimum caster level), so might not be worth it if I can't use the Potion Sponge.
Alter Self is 2nd level so I could get a swim speed for 3 minute duration at min caster level. Or my magus could learn it for a 5 minute duration.

Gronk de'Morcaine |

Alter Self gives at best a 30' swim speed (which gives the ability to breathe).
It is the best effect but only lasts for 3 minutes (or 5 minutes if I cast it).
I have a feeling we are going to be down there for fair bit of time. So I will have to also get the potion of water breathing.
But I think I'll want a alter self for a serious fight (or to run away).

Kolokotroni |

Air crystals are in the pathfinder society field guide. They dont appear in the prd, they are however on the d20pfsrd. I recently had an underwaterish encounter (black dragons lair) that we knew was happening. The alchemist that had formerly been with the party had made a bunch of these for us for underwater action. It doesnt last long, but it can actually be very helpful since it allows you to breath normally for a minute, you can hold your breath then chew an air crystal, then hold your breath again/repeat as needed. Greatly extending your effective time underwater if you have a descent con.

Snowleopard |

Depending on how deep you must go. My party went after a sunken wreck treasure last session.
3 of our 5 party members went down the depts to explore. And the remaining 2 were minding the boats and holding a rope with a grappling hook in case we needed to pull something up.
Don't forget to think of a rope code before you submerge (we did).
1 pull = more rope, 2 pulls = pull up.
While down our party noticed a aquatic monster that noticed our submerged party long before we saw it. And 2 succesfull attacks and a hasty swim upwards, resulting in 17 damage and 21 damage for our heroes made us decide to return later.
Next day we returned with our best preperation available. We used our best constitution guy (monk) who had a decent swim skill and a ring of swimming (+5 swim). We spelled him up with a Bull's strength, a potion of invisibility, my ranger's Negate Aroma spell and my ranger's Magic Fang spell. It allowed the Monk about 3 minutes of time submerged if not attacked and a 1.5 minute minimum. (The magic fang wasn't neccasary, but I cast it just in case).
Even in combat him rolling a one would have rolled him a 15 for his swim check.
The idea was to avoid any combat and simply get to the treasure and take it along. we now knew there was a monster down there, which was guarding the wreck. But it was too big to fit into the wreck. It was very perceptive though and we didn't know if it had the scent-ability or maybe even tremor-sense, which translates to underwater-tremor-sense for aquatic creatures.
We got lucky as it actually had scent, but not tremor-sense and combined with the potion of invisibility and the negate aroma spell the monster literally swam 5 feet past our monk and not discovering our monk while rolling a 20 on it's perception check.
We also had a grappling hook and rope in the water to lift the treasure or our monk back up. We gently lifted the treasure chest out of the wreck and rowed out as fast as we could.
It was a great coorperation with my Ranger's spells, our freshly conquered potion's of invisibility, our Cleric's bull's strength and swim ring which he loaned to our Monk. Our Barbarian massive strength for lifting the treasure from the wreckage. And I guess our thief was there as well and she managed to open the chest without force after we retrieved it. So it actually was a full party effort, which made the undetected swipe even more fun. We got 1k in gold and adamantine machete which will be nice going into the jungle.

Mudfoot |

Can't really use scrolls underwater.
There's no intrinsic reason why a scroll has to be made of paper, or otherwise be harmed by water. It'll probably cost more in materials to make a waterproof scroll, and the GM might require some research, but ultimately I can't see why it shouldn't be allowed.

Umbranus |

My search isn't finding a Diver's Kit. Which book has that?
Kit, Diver's
Source Dungeoneer's Handbook
Price 121 gp; Weight 38 lbs.
This kit is ideal for adventurers who venture into sunken ruins or half-flooded temples, and includes an air bladder, a common buoy, 30 feet of chain, a fishing net, a glass bottle, a pound of soap, three sunrods, a waterproof bag, and a waterproof hooded lantern with 3 flasks of oil.
Not much in it beside the obvious.