I left my frozen whole chicken (about 3-4 lbs) in cold water overnight by accident. I am going to boil it for soup. Is it still ok? 
The answer to this is the same as the answer to every food safety question involving meat and other highly perishable foods:  how long as it in the danger zone (40 - 140 F, approximately 4 - 60 C)?   If it was in the unsafe range for more than 2-4 hours, it is a risk.  The higher the temperature within the zone, generally the riskier it is.  You must assess how large a risk you consider that to be.  I certainly would not have anyone at risk (children, elderly, compromised immune systems) eat the chicken.  I would not eat it myself, unless the water was 40 F or lower--that is quite cold--but if that is the case, then it was essentially refrigerated under water, which would be fine.  If you were operating a restaurant, you would certainly be required to discard the food if it was left in cool room temperature water overnight. 