I have found warm water to be a great way to quickly defrost meat and fish as opposed to just letting it sit outside the freezer, which is what my mom does.
But I wonder if there are any negative side effects to the method, as in, for example, compromised taste or compromised food safety. I do understand that the water shouldn't be too hot as to avoid actually cooking the frozen food.
Best Answer
For a small fillet of frozen fish in a ziplock bag, this method will be fine because any single serving fish fillet will only take 10 minutes or even less to defrost in warm water, and will take even less time to cook. However, as described in other answers, you cannot extend this method to larger cuts of meat like a massive t-bone steak or a giant chicken breast.
I use this method to defrost tilapia fillets and salmon fillets all of the time, but I am very careful to cook them after a few minutes of defrosting. I find that for thicker salmon fillets I only defrost it half way (about 5-10 minutes) and immediately throw it in the pan with the center still somewhat frozen. This prevents you from overcooking the fish, and still prevents you from keeping the fish in the danger zone too long.
If you would like to use this method on thicker cuts of meats, you can modify it where you use a Tupperware container full of cold water and place it in the fridge. It will defrost faster in the water than it will not placed in water, and the fridge will keep it out of the danger zone (of course this method takes longer).