Place the fish in a plastic bag and tie the bag in a knot to completely seal it. You don't want the water to actually touch the fish. The cool temperature of the water will be able to thaw the fish through the bag. If the fish floats, put a plate or another weight on top to keep it completely submerged. The fish will thaw quickly in the cold water. Let it sit for about an hour to make sure it thaws completely before using.  As an alternative, you can run the fish under cold running water to thaw it out. The water doesn't have to run rapidly; a steady stream will do. This will defrost the fish more rapidly than placing it in a pot of cold water. However, use running water only for thinner fish filets, since you don't want to waste too much water by running it for half an hour or more. Check the fish to see whether it has completely defrosted by pressing your finger against the flesh. If it still feels frozen in the middle, let it continue to thaw. Don't thaw fish in hot water. This will thaw the fish unevenly and too quickly, changing its taste and texture. 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. Use the “defrost” setting in your microwave as an alternative to icy water. Place your fish in a microwave-safe container and defrost it for several minutes. Check on the fish often, and stop the defrost cycle while the fish is still icy but malleable.  Use this method only if you're planning to cook the fish immediately after thawing. Be careful not to actually cook the fish in the microwave; take it out while it's still cold to make sure the texture and flavor don't start to deteriorate.

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Write a summary of the previous text in Vietnamese:
Bọc cá bằng túi nhựa. Cho cá vào chậu nước lạnh. Cân nhắc việc rã đông bằng lò vi sóng.