Sure it's possible - put the fish in a bag of water and place that in a styrofoam lined box. Depending on the weather you may need to add a heat pack or a cold pack to fight the temp creeping in whatever direction it is supposed to go. I like the breather bags from kordon - they allow gasses to be exchanged while keeping water in the bag. Because of this you don't have to ship in such a large container, and because there will only be a small amount of air space in the bag, less sloshing around for the fish in transit.