It is worth saying plainly who the phrase referred to. These were people — men, women and children taken from West and Central Africa, packed into ships that were already illegal under their own country's law, and unloaded onto sand at night under a layer of poultry crates. They had names nobody here wrote down. The traffic did not slow after 1831; Britain's Aberdeen Act of 1845 let the Royal Navy seize Brazilian slave ships, and the effect was a panic buying spree, with the largest arrivals of the entire illegal period falling in 1847, 1848 and 1849. Brazil finally shut the trade with the Eusébio de Queirós Law on 4 September 1850, and abolished slavery itself only in 1888, the last country in the Western hemisphere to do so. Both the municipality and the standard reference works tell the etymology this way, without hedging. The town has kept the name. It is a beach resort's cheerful, slightly comic label, and it is also a receipt.

What draws the crowds is a geological accident. A line of sandstone and coral reef runs parallel to the shore a short way out, and when the tide drops far enough the reef surfaces and the water trapped behind it becomes a chain of clear pools — the piscinas naturais, said to be the closest natural pools to the coast anywhere in Brazil. They are only there for about two hours a day, at very low tide, and the schedule shifts with the moon, so the whole town organises around a tide table. Jangadas, the flat sailing rafts of the northeastern coast, ferry visitors out from the beach in relays. Snorkellers who have swum Hawaii or the Riviera Maya sometimes come back unimpressed by the fish count. Nobody comes back unimpressed by standing chest-deep in warm water a kilometre from a bar.

Walk south along the sand and Porto quiets down into Maracaípe, which has surf where Porto has none, and kitesurfers working the wind off Pontal do Maracaípe. The Pontal is also where the mangroves start, and where a protected breeding area for seahorses sits in the estuary — the Recanto do Cavalo Marinho, reachable by jangada, and dependent on visitors keeping their hands to themselves. In midsummer, on full-moon nights, sea turtles come ashore on these beaches to nest. Locals plan around it the same way they plan around the tide.

Porto de Galinhas is roughly sixty kilometres south of Recife as the crow flies and about eighty by road, which makes it the default weekend for Recife and everyone in its metropolitan area. Buses from the Cais de Santa Rita and from the airport run from before five in the morning until half past ten at night. On Saturday the pracinha — the little square where the two main streets meet the beach — fills with bands, and the pousadas closest to it stop being restful. Buggies wait at the top of Rua da Esperança to run people down the coast. Carts on the sand sell piña colada served in the pineapple. Readers of the Brazilian magazine Viagem e Turismo have voted this the best beach in the country year after year, citing the pools, the trails, the hotels and the short drive from an international airport, and the voting has become part of the brand.

The town has never traded the name in for something blander, and there is a reasonable case that it should not. The three words on the sign are the only part of this history that a visitor arriving purely for the snorkelling is guaranteed to encounter. Ipojuca was carved out as a district on 12 November 1895, seven years after abolition, and the coast has been rebuilt several times over since — pousadas into resorts, fishing beach into brand, and the industrial port complex of Suape rising a short way north. The name is older than any of it, and it is still doing exactly what it was built to do: carrying information about what arrived here, to anyone who knows how to hear it.