Cayo Arena offers schools of tropical fish that can also easily be seen in shallow turquoise waters, making this spot a paradise for snorkeling fans; the area boasts some of the most abundant marine life in the DR, with corals and sponges, and schools of tropical fish swimming around your feet.
Look out for manatees at the Marine Mammal Sanctuary in nearby Estero Hondo, an hour east of Montecristi, where a couple of hiking trails lead you towards a protected lagoon, home to the largest number of endangered herbivore West Indian Manatees in the DR. The Estero Hondo Marine Mammal Sanctuary also doubles as a protected habitat for birds–climb the lookout tower to spot manatees and birds in one fell swoop.