We just bought a red clawed crab from petsmart and they told us it can live underwater completely. I did some research when we got home and numerous websites say they need to be able to go on dry land too. We ordered a below the water habitat for it but it takes three days to get here, I'm wondering if it'll survive for three days underwater. Also can it survive in freshwater? because I've read that it can't but petsmart told us it can.

They can live in freshwater, but they do absolutely need some land. All you need to do until the other habitat gets to you is make some kind of ramp for it. Just something out of plastic or rocks or something.