Playa Grande in DR (btwn Rio San Juan & Cabrera) is probably the most beautiful beach I've been to.
I think my pics are on the upstairs computer and we're not networked, but here are one I googled (pictures really don't do it justice though...it was breathtaking!)...
http://www.drbeachrental.com/images/Img8.jpg
I've never felt sand so soft, or seen water so blue (I'm not an ocean person, but I went in up to my shoulders it was so beautiful!)