Three Methods: Thawing in the Refrigerator Thawing Fish Quickly Cooking Frozen Fish. Thawing frozen fish properly will help it retain good flavor and the right texture while also keeping it from becoming contaminated with bacteria. Don't thaw fish in hot water. 2  This will thaw the fish unevenly and too quickly, changing its taste and texture. 3  Thawing in hot water will also make the outer edges susceptible to getting contaminated with bacteria before the inside of the fish is finished thawing.