Fish should be thawed in the lower part of the fridge. If you want to thaw it faster, you can do it under cold running water, as long as the packaging is properly closed.
Do not thaw fish at room temperature. If you do, the fish’s appearance, aroma, texture, flavor and nutritional value may change.
Once thawed, the fish should be eaten as soon as possible and never be re-frozen.
If you intend to boil the fish, thawing is not required: place it directly in the cooking water, which provides greater nutritional utilization, safety and speed. If not for boiling, fish up to three inches thick must thaw in the packaging, at the fridge’s bottom shelf for a few hours.
Do not attempt to speed up the process by placing the fish directly in water, as that may cause the loss of some nutrients.
Source: Fileira do Pescado.