Playa Sosua is the town's main beach. It is a fun, colorful and lively beach which is approximately one kilometer long, with a row of shacks along the back, selling food, drinks and souvenirs. At one end of the beach is the El Batey neighborhood, which was founded by a community of about 600 Jews exiled here from Eastern Europe during WWII. It contains the small synogogue, still occasionally used by Jews from the surrounding communities, as well as a small museum documenting the history of the Jewish community in Sosua, both set in a tidy tropical green lawn adjacent to Casa Marina Resort. The synogogue has services on Friday evenings about once per month - check with the museum whether there are services the week you are there. Batey no longer has an active Jewish community and is currently the tourist section of town, containing several all-inclusive resorts, as well as a number of smaller hotels and guest houses.
At the other end of the beach is Los Charamicos, which is the local's neighborhood and somewhat more run-down and lively than Batey. For an authentic cockfighting experience go to Club Gallistico, in Charamicos. It is along one of the main streets but you will have to ask for directions. Cockfights are on Saturday afternoons and sometimes on other days of the week. It is best not to venture alone into the alleyways of Charamicos as they are unsafe. The main streets should be OK.
The beach is very popular and offers the best local option for the snorkeling enthusiast - snorkelers should swim out to the reef that lies about 100m from the shore. A beach chair rental should cost about RD$60. Refuse to pay any more. Equipment can also be rented there. There are lots of gift shops where you will be quoted absolutely laughable prices. 60 dollars for T-shirts, 50 dollar tote bags 150-200 dollars for some cheap Haitian paintings. Your bargaining skills will be needed. Tip: whatever they ask you, cut it at least in half, e.g., RD$500 pesos, you tell them RD$250.00 and start the process. You can probably even start at way below RD$250. You will come out ahead this way. My experience is that the target price for which the kiosk will ultimately settle is about half or slightly below half of the original asking price, but sometimes somewhat below that.
There are two other beaches in town. Playa Alicia is accessible from the On the Waterfront restaurant. This beach is quieter and more sterile than Playa Sosua, and is thus a good option for those who want to trade a bit of local color for a more relaxed experience. The town's third and smallest beach is accessible from the Sosua by the Sea hotel.