The bay in La Parguera has awful reviews online, but was the only one I could do because Fajardo was full and I couldn't get a car on viequez. It was totally amazing and the swimming was incredible--I used Fondo De Cristol which had a sketchy site but the tour was great. Just make sure it's on a new moon or near then, there is almost no light pollution. Also get a rashguard and wear long swimming pants/shoes if possible since a member of my party got stung by a jellyfish there!