Reserva Ecológica Rio Playa protects forest, swamp, and mangrove habitat north of Comalcalco. It is locally managed ejido land rather than a polished national-park experience, which is part of the appeal if you are interested in birds and wetland landscapes.
Go with local advice, especially after heavy rain. Trails, access, and transport can be less predictable than at the archaeological site, but the reserve adds the natural side of Tabasco to a visit built around ruins and cacao.