The Reserva de la Biosfera Pantanos de Centla visitor center, the Centro de Interpretación Uyotot-Ja, or ‘Casa de Agua, ’ is 13km along the road to the town of Jonuta, beside the broad, winding Río Grijalva. Here a 20m-high observation tower overlooks the awesome confluence of the Grijalva, the Usumacinta and a third large river, the San Pedrito – a spot known as Tres Brazos (Three Arms). Guides lead you round a nature trail and displays on the wetlands.
Boat trips (two hours, up to seven people M$1000), offered by a changing schedule of local communities, are available into the mangroves, where you might see crocodiles, iguanas, birds and, with luck, howler monkeys. These lanchas are rudimentary at best, so it's better value with a group. Note: these operate daily (while the Centro de Interpretación Uyotot-Ja does not). March to May is the best birding season.