At the northernmost point of Duarte you’ll find a beautiful mangrove reserve that you can explore through organized boat tours. You might have a bit of a hard time finding any operators by searching the web beforehand, so your best bet is to book these tours in person once on location. Campo Tours is the sole operator in Río San Juan but you can find better quality-tours and deals down the road in Cabarete. These two hour tours cost about $1,200/person RD but the price will vary slightly from one operator to the next. Once the boat has exited the lagoon through the mangroves, it enters Cueva de la Golondrina (Swallow’s Cave) where you can peep some stalactites and stalagmites. If you’re in the mood for a swim, you’ll have your chance to jump in the water near the coast of Playa Caletón – the water there is gorgeous.
Tip: Go early in the morning to catch more of the birdlife. It’s worth it!