São Marcos beach is in a more sheltered position than Calhau, facing the bay rather than the open Atlantic, and the water here is calmer and warmer. The beach is popular with families for this reason, and the calmer conditions make it better for swimming with children or for anyone who finds the open-ocean waves at Calhau too strong.
The beach has a good selection of kiosks and restaurants, and the surroundings are slightly more upmarket than the older beach areas. On weekday mornings it's quiet enough to feel like your own private beach. On Sunday afternoons it transforms into a social gathering of considerable scale.