This may be the best place in the Caribbean for some fun in the sun.The bright waters of Arena Gorda Beach in the Dominican Republic.Credit: Andrey Bukreev/Getty ImagesIf you’re dreaming of sunshine, powdery sand, and crystal-clear water after a long, chilly winter, it might be time to plan a Caribbean beach escape. But instead of picking just any shoreline, why not seek beaches known for their cleanliness and eco-friendliness?An easy way to do …