...Or, if you happen to miss the early bird ferry to Les Saintes, consider this beach your go-to option for an hour or so spent in paradisal bliss that you'd expect to have to fly thousands and thousands of miles to get to otherwise, it's so delightfully unkempt and unspoiled and often uninhabited.
From Trois Rivers town, take the road out of town that follows the island's southern shoreline, rather than going back up the giant hill to return to the main road. Keep an eye out for the signs for Grande Anse Plage; it's not too far. The sand is fine and the water can be a bit rough, but for that moment of "where am I actually in the world right now?" this beach has all of that feel.
A tip: All of the beaches in Guadeloupe are marked with road signs, and any that I've ever turned off to find are worth the detour, whether you stay for lunch, for some splashing and sunning, or simply to admire the view for a few.