the beaches are nice as far as looking at them. they are beautiful and pretty clean, etc. but it is the swimming that is more difficult.
up north it is more pristine. here are photos from journey's end: (keep in mind it was before the hurricane hit): http://ambergriscaye.com/jane
however, it was pretty shallow fairly far out (i didn't care, there was a pool too). the water was very clear, and you could kayak out, tie up & swim or snorkel at the bouy, like we did.
swimming off ramon's pier near town is popular with first time visitors.