Sosua has a lot to offer if you are looking for experiences.
Don't miss Castillo Mundo King, surely the most bizarre museum in the world, offering 5 floors of art, primarily space themed.
At the city beach of Playa Sosua you can find coral reefs and many paid services, excursions - fishing, diving, snorkeling at Los Cabezos or 3 rocks, and for me the less interesting sunken statue of Atabay.
For horse lovers, visit the Sea horse Ranch, where you can ride a horse. In addition, every Saturday there is a Food Market from 10:00 a.m. to 1:00 p.m.
For sunset, people like to go to Laguna Costera. It is a coral reef on the outskirts of the city, where if you are lucky, you will come across a small crater lake created by high ocean waves. You can also bath there.
If you need a change from salt water, you can visit one of the water parks in Sosua - Santa Fe, Laguna SOV and Waterworks Waterpark.