The signature experience in Huacachina, and the reason most travellers come. Souped-up dune buggies leave from in front of every hotel in the late afternoon, climbing the largest dunes around the oasis and then diving down the far sides at terrifying angles. Between runs, the driver stops on a crest and hands out sandboards: lying face-down headfirst is the fast, easy, sandy option; standing up like a snowboarder is harder than it looks and not really worth it.
Tours run about two hours and are timed to finish at sunset on top of a high dune, with the oasis far below and nothing but rolling sand to the horizon. The standard cost is around 60 to 80 soles per person depending on group size; every hotel and hostel sells essentially the same tour using the same handful of buggies. Bring sunglasses, a scarf for the sand, and clothes you don't mind ruining.