Does fish partially cook, if you defrost it with hot tap water?

No it does not, unless it was precooked don’t eat it. Fish is naturally flaky and colored that way. You could get sick if it’s not probably cooked.

Yes, it probably did partially cook but would need to be fully cooked. Best to defrost it more slowly in the fridge and then cook it as you would like.

Used to work in a fancy Italian restaurant where we served seafood, had to defrost. Always use cool running water to defrost, as hot won’t cook fully but will start the cooking process.

Yep. That’s why it changes color. You’re basically doing a short, sous vide. Cooked fish starts around 125 degrees F, so I’m not surprised the water partially cooked it.

I wouldn’t eat it though. It feels a bit too danger-zone.

@Smashley You’re basically doing a short, sous vide

Exactly. You are under-cooking the fish, similar to baking it at 350 F for 10–15 minutes.

Sous vide hot water cooking is legit. I tried it with an insulated cooler and boiling water, making chicken breasts. It worked but I missed the sear and browning that a stove or oven provides.

But try it yourself. It is inexpensive. Here are a couple of guides I googled up:

How to Cook Food in a Cooler: 6 Techniques to Consider

Cook Your Meat in a Beer Cooler: The World’s Best (and Cheapest) Sous Vide Hack