Mang Beach is one of Petite Martinique's easier swimming spots, with calmer water than the more exposed Atlantic-facing edges of the island. It is not a serviced beach in any resort sense, so bring what you need and leave the place as you found it.
The appeal is precisely that simplicity: clear water, village life nearby, and views across to the neighbouring Grenadines. Conditions can change with wind and swell, so ask locally before swimming far out.