There’s an old Jamaican expression that belongs naturally on a Caribbean beach: walk good. It’s usually a goodbye, a wish for safe travels, a simple way of telling someone to take care. It also describes one of the Caribbean’s simplest pleasures: putting your feet in the sand and walking until it’s time to turn around. Summer is starting to wind down, and fall Caribbean trips are coming into focus. The crowds change, the heat starts to ease in parts of the region, and a long beach walk starts sounding even better. Some beaches are made for a swim. Others are small coves where a towel,...