Culebra is smaller than Vieques, and the water is often clearer. Flamenco Beach is the one in the photos. Luis Peña is the everyday snorkel. Dive boats run when they have a group. There's no Mosquito Bay here. Come for the water, not for a night glow. Region page: Vieques & Culebra.
Beach days that actually stay on the island
Flamenco can fill with day-trippers when the ferry behaves. Early is quieter. Scuba is a shop product with boat minimums, not a drive-up shore circuit. Give the island a night so you're not watching the clock.
Booking on adventuro
Snorkel trips are beginner-friendly if you swim. Open the Book here tab. Build slack before any SJU departure the next day.