Most of the prawns sold in Lagos are frozen. Its obvious when you see packs and packs of prawns in the massive freezers at supermarkets. Did you know that even in the open air markets where the prawns are weighed and sold to you looking all limp and fresh from the sea, the some of the merchants get boxes and boxes of frozen prawns from trawlers and thaw them out with water and sell? Freezing is a preservative method so there isn't anything fundamentally wrong with frozen prawns. Its just that seafood should be as fresh as possible for best results in your recipes and sometimes, one doesn't know how long the packed prawns have been sitting in those freezers. Freezer burn doesn't translate well to food.
To refresh frozen prawns, rinse them in cold water with a tablespoon of salt. This process is like magic. The prawns get that fresh from the sea look and any sign of freezer burn is gone. So easy to do and well worth making this a part of your kitchen repertoire.