There is an endless maze of mangroves to explore in the estuaries of several rivers that empty into the sea near Boca Chica. But most come here to enjoy the islands.
Isla Boca Brava is the closest to Boca Chica. The island is 14 kilometers long, six kilometers wide, and overflowing with wildlife. It’s right on the edge of the park.
Because of the rivers on the mainland, the water gets clearer the farther away one gets from shore. The closest uninhabited islands are Linarte, Saino, and Las Ventanas (ventana means window; the name refers to the caverns that run straight through their rocky sides).
But the best islands are farther out. The snorkeling is decent around Isla San José, a short boat trip away, but it’s definitely worthwhile to head out even farther.
Isla Bolaños is 13 kilometers from Boca Brava, about 45 minutes by small boat equipped with a decent outboard motor. This is a lovely little deserted island with a couple of sandy beaches, lots of coconut palms, and snorkeling when the tide’s low. This is one of the best places to see humpback whales and their young between August or September and November.
Twenty minutes from Bolaños is Isla Gámez (sometimes spelled “Gámes”), also lovely and even smaller. This one, however, tends to attract yachts and the weekend personal watercraft crowd, while Bolaños is rarely visited. (Sadly, though, even Bolaños has its share of trash.) Both these islands are tended by the nonprofit environmental group ANCON.
Isla Parida, just across from Gámez, is a big, inhabited island with lots of trash and can easily be skipped. There’s an ANAM station on Parida next to a bunch of ramshackle huts and a dirty beach. You can spend the night at the station, but it’s hard to see why you’d want to.
The scuba diving is said to be terrific around Islas Las Ladrones and Islas Secas, where the water is clearest and the sealife the richest. The diving visibility can be up to 30 meters at Las Ladrones. The islands are very far away: Las Ladrones islands are 40 kilometers southwest and the Islas Secas 30 kilometers southeast of Boca Brava.
Do not attempt to go this far on the open sea without something more substantial than the little pangas common around here. If you do find a way to get there, the snorkeling should be good, too.
There is now a high-end resort  on the Islas Secas. Though it’s expensive, staying there is by far the easiest way to get to and explore the islands.