Balneario Santiago (Carr. 3, km 72.4, Humacao, 787/852-1660 or 787/852-3066, Mon.–Fri. 7:30 a.m.–3:30 p.m., Sat.–Sun. and Mon. holidays 7:30 a.m.–5 p.m., $3 cars, $2 motorcycles, $4 vans, $5 buses, camping $25–40) is a great stretch of publicly maintained beach and vacation center with a swimming pool featuring a big waterslide, modest overnight accommodations, camping facilities, bathrooms, and picnic shelters.

Adjacent to Balneario Santiago, along about km 68.3, is a large shady wilderness beach that is unfortunately heavily littered and crawling with feral dogs. On the weekends you can find vendors there selling beverages, trinkets, oysters, and other food items.

From here you can see Cayo Santiago, also known as Monkey Island because of the large population of rhesus monkeys placed there for safekeeping by animal researchers. Visitors are not allowed on the island, but they’re welcome to dive and snorkel around its edges and watch the primates from a distance.