I was wondering if anyone who has played the first adventure in the campaign could answer a question of mine. I am in the middle of redesigning my tiefling character into a rogue, and I wanted one of my two traits to grant a bonus on swim checks. My question is, which is better for Skull and Shackles? A +1 damage bonus on daggers (which I will be using a lot of) or a one point reduction on attack penalties underwater?
Whichever makes most sense for your character in terms on concept. I don't usually say that as an answer to a question like this, but frankly, both bonuses are extremely "corner case."
River Rat gives you +1 damage with daggers. Unless you are using daggers for another reason, all that does is make them approximately equal to short swords. Rogues are already proficient with both, so unless you plan to throw the daggers or use the Knife Master archetype, you aren't getting much of anything out of the deal.
Touched by the Sea gives a reduction in penalty, but that penalty doesn't honestly come up that often. It only matters if you are using a slashing or bludgeoning weapon, or if you fail your swim check while using a piercing weapon. Bludgeoning and slashing weapons still have their damage cut in half underwater, making them terrible choices in this situation. Take a piercing weapon, have a passable swim check, and this situation will simply never come up.
In the end, the only difference is the ever ephemeral "flavor." Touched by the Sea is probably easier to explain than River Rat, but they are quite close to equal. Unless someone glances at your character sheet, I doubt anyone at the table will ever be able to figure out which one decided to take.
EDIT: I got a bit off track from the specific question. River Rat might be slightly, slightly better for the first adventure, in that a dagger is a bit easier to come by than a short sword. There are a couple of opportunities for underwater combat, but if you are in a situation to take a penalty on it you are probably going to be dead anyway. I'd still side firmly with "whichever matches your flavor."
Thanks for the help, Mort!
Daggers are also easier to conceal, which comes into play a few times in the first adventure, and probably afterwards. (Or so I'd imagine.)
As for River flavor, the riverfolk out east of Varisia have a set of interesting tenets which are heavily freedom-seeking (which often translates as 'easy on thieves'). I could easily see someone from out that way wandering south for adventure and experience, maybe getting into trouble with Cheliax (totally un-freedomy) and escaping into the Shackles. This background has the added benefit of making you totally unaware of press-ganging, or simple skeptical that any pirate (being defined almost essentially by the liberties they take) would actually enslave another.