That's why, in the past, I've packed the fish baggies into a 'small' lock-top cooler, taped it shut and then boxed the whole thing up with plenty of packing material to cushion things if dropped. The cooler keeps the water where it belongs, protects the fish, and keeps the temperature from fluctuating too much. The price of the cooler is neglegible when it does such a good job getting the fish to their destination.