Kanmuri-san no Tokei Koubou - Vol. 1 Ch. 4 - The Water Has Got In

[MangaDex]

 

[Kaarme]

With fresh water intrusion, maybe one could open the watch and then place it in a sealed chamber with regenerated silica gel. That ought to dry it efficiently. Though maybe lubrication would still be needed. It's also possible the water could have carried minerals to glass surface, which would remain there as stains after the water is gone.