The name is Tupi. Jenipabu comes from the words for the jenipapo fruit and for water — river of jenipapos — a description of a place that existed long before anyone thought to drive across it. The dunes sit in the municipality of Extremoz, about twenty kilometres north of central Natal, close enough to be a half-day trip and far enough that the city stops feeling like a city on the way. Greater Natal keeps creeping north toward it. For now the last stretch still arrives the way it always did: through low coastal scrub, and then abruptly onto an open field of sand with the Atlantic on one side and a freshwater lagoon on the other.

These are mobile dunes, and the phrase is literal. The trade winds along the Rio Grande do Norte coast blow hard and blow constantly, lifting sand off one face and dropping it on another, so the field slowly walks. A crest that dominated the skyline a decade ago may be a hollow now. Nothing here is a permanent landmark, which is part of why the driving is regulated — only operators certified by the state tourism board are allowed to take vehicles onto the dunes, and the area falls inside a designated environmental protection area. The rule protects the drivers' livelihoods and the landscape in roughly equal measure.

The best thing at Genipabu costs almost nothing and involves no engine. Esquibunda — roughly, ski-on-your-backside — means sitting on a wooden board at the top of a dune above the lagoon and letting gravity do the rest. You accelerate faster than seems reasonable for a plank, hit the water, and come up laughing with sand in places sand should not be. It is also the only genuinely effective way to beat the heat here, where the sun comes off pale sand from every direction at once. Late in the day the crowd shifts to the high crests, because the dunes face west across the lagoon and the sunset from up there is the reason a lot of people came.

For years the postcard image of Genipabu was a dromedary train plodding along a ridge — imported animals working a Brazilian dune field, incongruous enough to become the region's signature photograph. The rides were popular for a long stretch of decades. They ended in the 2010s, and by 2020 they were no longer offered at all. The postcards have outlived the practice, which means visitors still turn up expecting camels and find buggies instead. It is worth knowing before you arrive, if only so the gap between the brochure and the beach does not sour the morning.

Down at the waterline the economy is straightforward. The shacks on the sand serve cold drinks and food at prices calibrated to people who have just spent a morning being thrown around a dune, which is to say high. Locals eat at the cheap set-lunch spots clustered around the Santa Rita bus terminus at the south end of the beach instead. Buses run from there back into Natal, some over the Newton Navarro Bridge — quicker if you are heading for Ponta Negra — and others by the older upriver crossing. Most visitors come by buggy and leave by buggy. Coming back on the bus, with sand still in your shoes and the dunes shrinking behind you, is the cheaper and slightly more honest version of the trip.