Parque Las Croabas (Carr. 987) is a pleasant waterside park overlooking Bahía Las Croabas, dotted with moored fishing boats. From here you can see the island of Vieques [1]. There are several concrete picnic shelters, poorly maintained bathroom facilities, and a small boat launch. Across the street are several bars and restaurants serving seafood.
Links:
[1] http://www.moon.com/destinations/puerto-rico/vieques-and-culebra/vieques