Playa Chica is Tarifa's small, sheltered town beach, tucked between the port and the causeway to Isla de las Palomas. While the Atlantic side is about wind and long sand, this little Mediterranean-facing cove is often calmer and better for a straightforward swim.
It gets busy because it is so easy to reach from the old town. Bring a snorkel if the water is clear, then walk the short distance to the island causeway for the satisfying sense of standing between two seas.