The malecón is the human centre of Catazajá: the place to arrange a boat, eat fish and watch the lagoon instead of hurrying through town. "Playas" here means the waterfront rather than a classic swimming beach, so come for water, breeze and boats, not white sand.
It is at its best late in the day, when the heat eases and the lagoon catches the light. Ask locally about boat conditions and wildlife before paying for a trip; water levels can change the experience a lot.