Puerto-Rico

Playa Sucia sits at the very corner of Puerto Rico, a crescent of pale sand enclosed by cliffs, with water that is usually calm and remarkably clear. The name means dirty beach and refers to seaweed that drifts in on some winds, not to the water. Above it a short uphill walk on exposed limestone leads to the Los Morrillos lighthouse and cliff edges that drop straight to the sea - spectacular, and completely unfenced, so young children need holding. Nearby are the pink salt flats of the Cabo Rojo salinas and a birding boardwalk. Bring everything; there are no facilities.

Puerto Rico is the easiest Caribbean trip an American family can take and the one most people plan badly. It is a domestic flight with no passport, dollars, and your normal phone plan — and then people book San Juan for a week and see a fort. This is four days built around the one thing you cannot reschedule: the bioluminescent bay. Plan the trip around the moon, not the weather The bio bays work by dinoflagellates flashing when the water is disturbed, and what kills the effect is not cloud or rain — it is moonlight. Tours run around the new moon and are thin to useless near a full one. Some operators will not run at all. ...

Sun Bay is a public balneario, which means facilities - restrooms, showers, shelters, a large parking area - attached to a beach that on most days is close to empty. The bay is broad and shallow with very little wave action, so it suits small children, and the sand runs for over a mile so you can always walk away from whoever else is there. Vieques’s free-roaming horses graze the grass behind the beach and wander onto the sand, which is one of those things children do not forget. Camping is permitted with a permit. It is the easiest beach on the island to reach with a hire car.

Tamarindo is not much of a sunbathing beach - narrow, some rock, modest sand - and that is not why anyone comes. Just offshore the bottom is turtle grass, and green sea turtles graze it reliably enough that a morning snorkel here is close to a guaranteed encounter. They are unbothered by swimmers who keep their distance, and the water is shallow and generally calm. There is also decent reef towards Luis Peña Cay. There are no facilities at all, so bring water and gear. Regulations require keeping a respectful distance from turtles; do not touch or chase.