I've found 5 bottles so far. One had the swords motif (the motif includes one and two handed sword crafing), one had the shoulder motif, the other 3 had sea serpent skin.
This may or may not have any bearing, but the two that had motifs were found in river fishing holes. I've fished the coast from Alinor, moving counter clockwise along the coast, and stopped at the North end of Summerset. When I got to the northern part of Summerset I found 3 bottles. The 3 from the sea coast had Sea Serpent Skin. This was the first and, thus far, the only time/place I've found Sea Serpent Skin. Maybe just a coincidence, but the *Sea* Serpent Skin were found in *sea* fishing holes. And as I wrote, my motifs were found in rivers. Could just be anecdotal though.
I've had the best luck with worm bait, guts were second best. I had crap resuts with crawlers, insect parts, minnows, and one other bait I can't remember the name of right now. Really, I just use worms and guts, and of those two, worms really. I've gotten one epic salmon, blue quality scallops (or some similar shell food), and a ton of green quality fish.
Other baits either produce used bait or common quality longfin and some fish that starts with the letter "d". It's common af. So much so, I don't even bother to remember the name. Ain't worth my brain's memory space. Lol