The southern approach to Doñana is by river. From the Bajo Guía waterfront in Sanlúcar de Barrameda, tourist vessels run up the Guadalquivir into the park's southern boundary on boat trips that typically last three to four hours return, with guided walks into the park at the landing point. The perspective is entirely different from the northern 4x4 tours: you arrive silently, the riverbanks are thickly wooded, and the transition from working port to national park happens gradually, marked mainly by the disappearance of buildings and the thickening of bird life on the water.
Sanlúcar is itself worth visiting. The town is celebrated for manzanilla sherry — a bone-dry fino style that only develops its distinctive chamomile character within the town's humid, sea-facing cellars — and for langostinos from the Guadalquivir estuary, considered among the finest in Spain. The Bajo Guía strip of seafood restaurants is the obvious place to eat before or after a tour. Book boat places in advance, especially in spring and during August when Spanish domestic tourism peaks.