Huacachina is a small oases in the middle of endless gigantic sand dunes. It's a great place to relax, which is exactly what we did here the first day.
On the second day we decided in the local pass-time, sand boarding. You get driven around the desert in sand buggies for a while, up and down the dunes, until they spot a dune that looks like it has good boarding potential. Then you strap yourself onto the board, much like a snowboard, and proceed down hill, getting sand absolutley everywhere! Great fun, and it didnt really hurt when you crashed either. We only managed the technique where you dont really stand up, just crouch and put a hand in the sand behind you for balance. Maybe we'll try the world's highest sand dune when we get to Nazca!