Strange Sub watch cleaning advice

[realest145]

I met someone at a coffee shop a few days ago and he made a nice watch comment to me. I said thank you and he showed me his matching watch. During our conversation he said that he was told 15 years ago when he bought his that once a year you should submerge your Sub in water over night then clean it with soap and water the next morning. I am assuming that the point of this would be to remove any dirt, grime, etc. that is hardened on the watch and give it a deep clean of sorts once a year. I have never heard of such a thing. Anyone have any thoughts on this???