I have not seen this in any walkthroughs, but there is a way to complete Regrets Worth Trading (quest in Stalwart to get Okrun's heirlooms back) without having your character dive in the pond and potentially get injured. I am doing a solo run with a low-con rogue, so coudln't cast protection against elements and couldn't dive in the pond without either a way to raise my con way up from 3. Eventually I was able to raise it up to 11 (belt of +3 con, reset with +3 con bonus and eat chicken which gives another +2 con). I don't know if I can still dive in the pond with my constitution being 11, but by that point I took out a group of bandits north of Galvino's cottage in Durgan Battery (they are kinda in the dead-end of the road there), and they had a notebook on getting giftbearer drops out of the pond. There is a lagufaeth which lives in the pond, and it can be convinced to bring stuff up in exchange for fish (which fortunately I had in my inventory). So, the order for this quest is after you discover the location of the drop - take out the bandits north of Galvino's cottage in Durgan Battery (if you haven't already done so), and read the note they drop in the loot. Then comeback to the pond. Choose dialog option Xonton Tilla (it calls her up), then Cuallo Tilla (praise her to encourage her to swim), then the third Tilla option you haven't used yet, when she comes back up, say Cuallo Tilla again and give her some fish. There, now, you have the chest from the bottom of the lake even if you are a low-Con rogue.

There is a potion you can drink as well to protect you.

Good that you tell her... one year after she posted. 😄