Found an iPhone submerged in a river, what (if any) components may be salvageable?
It depends. Other then testing each individual part, no one could really say. What I'd do is take the whole thing apart, rinse everything off with water (distilled would be best, but at this point it probably doesn't make a difference) and clean everything with isopropyl alcohol. Dry everything off and reassemble the iPhone. Try to power it on. If it powers on, take note of what still doesn't work and email the Apple ID associated with it (maybe you could get it back to them and charge a repair fee, they may also just let you keep it and, if they're VERY trusting, let you use their Apple ID password to take the iCloud lock off of it). If not, sell it as-is on eBay, where, depending on the model, you still might get $100+, $200+ for it.