Agua Hedionda is Cuautla's best-known bathing complex, fed by sulphurous mineral water that gives the place its blunt name: "stinky water." The main pools are large, lively, and popular with families, with slides and smaller private pools around the complex.
It is more local day out than polished resort, which is part of the appeal. Go for a swim, look for the mermaid mural, and do not expect the smell of the water to be subtle.