In parks, oysters are accustomed to be outside of water several hours a day depending on the tides, and whatever the time: therefore, they are not too fragile.
Oysters can be kept at a cool temperature: favoring an unheated room. You can also put them in the bottom of your refrigerator, they do not fear the cold. They tolerate frost and if you left them out on your balcony and are frozen, you bring them to room temperature and you can appreciate them without risk..
You must keep them flat and not upside down so that they retain the water inside the shell. Oysters are packed by hand: they are always well positioned when you buy them packaged. You keep them in the original packaging (wooden crate), remove only the plastic that is used to transport.
In good storage conditions, oysters can be stored for ten days or more. As long as the shell is closed the oyster is consumable. If the shell is a little open, test if the muscle retracts with lemon or with the tip of a knife, you will be totally safe.