How to freeze fish?

There are different options to freeze fish.

Whole fish gutted and cleaned: the best method for freezing fish is to vacuum-seal. Wash the fish well, place the fish in an airtight, vacuum sealed or plastic freezer bag.

Second method is glazing the fish. Is great option to keep the taste and texture of the meat but is kind of hard and take several times.

Dip the fish in cold water, place it on a sheet pan, and put it in the freezer until water is frozen. Pull the fish out and dip it again in water and place it back on the sheet pan in the freezer. Repeat this process until there is one quarter inch glaze on the fish. After that place the fish in a plastic bag and store it in the freezer.

Other option, easy but not the best is wrapping the fish in plastic wrap.
Wrap the fish (individually if you have more than 1), in plastic wrap, place it in a freezer bag and get rid of the air as much as possible from the bag, seal it and freeze it.

For fillet of fish, you can individually wrap it tightly in a heavy, protective plastic film, try to not leave any air bubbles and store in the freezer as soon as possible.

Check how long can you store frozen seafood here.