This lagoon at the northern end of Calle Duarte is fairly picturesque, with a dozen or more boatmen offering hour-long tours (US$50 for up to seven people) through tangled mangrove channels, including interesting rock formations and a cave populated by hundreds of swallows.
Look for a small shack next to the public bathrooms down by the Laguna – you’ll find it easier to join a group on weekends, when Dominicans come to take this trip. You can also visit the lagoon on foot – there’s a path on the far side of the Hotel Bahía Blanca along the water’s edge into the mangroves.