Rio Preguiças is a calm, slow-moving river in the state of Maranhão, Brazil, flowing through a landscape where river, dunes, and Atlantic coast converge. The river runs from the interior toward the coast, passing through the dune fields of the Pequenos Lençóis Maranhenses before emptying into the sea near the village of Atins and the sandbank of Caburé. The town of Barreirinhas serves as the primary hub for river access, with a pier that functions as the main departure point for trips heading downstream.

The river's current is gentle throughout, making it well-suited for kayaking and canoeing at most skill levels. A popular multi-day paddling route runs downstream over two days, typically organized as an autonomous descent from Barreirinhas toward Atins. This route passes through riverside communities populated by local fishermen, and the dune fields of the Pequenos Lençóis Maranhenses are visible along the banks. The delta area near Atins features feeder creeks and mangrove habitat that can be explored by kayak, with tidal conditions influencing the best timing for excursions in that section.

Key stops along the river include the village of Vassouras, known for seasonal lagoons that form during the rainy months, and the village of Mandacaru, where the Preguiças Lighthouse offers elevated views over the surrounding river, ocean, dunes, and vegetation. The sandbank of Brasília, across the river from Atins, provides a base for kayak exploration of the delta. Caburé, near the river's mouth, is a beach destination accessible by boat.

Wildlife along the river includes capuchin monkeys in the Vassouras area and guará birds (scarlet ibis) observed in the Barreirinhas-to-Atins stretch. The mangrove sections near the delta add ecological variety to the lower river corridor.

Kayak rental and guided descent trips are available through local operators based in Barreirinhas and Atins, with two-day self-guided descents a common format. Motorized voadeira boats also operate on the river and are used for day tours, so paddlers should be aware of motorboat traffic, particularly on the main channel.