Agiba Beach is the pride of Marsa, even if it is no more than 30-40 metres long. It is set between protecting cliffs, and a nice reception area has been built on top on one of these. The sand is cleaner here, and the temperature cooler. But the day ends earlier, as the cliffs take away the sunset hours. But when the clock closes up to 4, climbing up the cliffs is a nice idea, and the views over the coast to the east are stunning.
Not Agiba beach, but next to it. It is long and wide, and a good second option should Agiba beach be too crowded.