Transporting live crawfish is illegal in many states. This is because of illicit introductions of them into streams and lakes, and the introduced species may displace the native species or cause some other undesired effect. Flash freeze them before transporting.
Do not put them a cooler of water, the will use up all the oxygen and die rather quickly. Keep them cool with some ice on top and bottom , preferably left in the bag, but do not let them sit in water. What is RGV?