While visiting London last month my friend and I got caught in a soaking rainstorm and I had forgotten that I'd left my passport in my rucksack, which also got soaked!!
I did not discover this until we got back to our hotel room. Immediately I blotted what water I could, then stood the passport on its end to facilitate its drying out. By the morning, it was dry, also with a little help of the hair dryer in the room.
I was worried that upon re-entry into the US I would be questioned about the speckles on my passport photo page, but nothing was said. The barcode and my photo and vital info were not disrupted, so I guess the IO thought everything was ok and welcomed me back home.
Did quite freak me out though, this experience!