Dahab's coastline is more reef than sand, which is great for snorkeling but means you will not find wide stretches of soft beach like Sharm el Sheikh. The main swimming and sunbathing happens at the Lagoon, a shallow sandy bay about ten minutes south of town that is also the hub for windsurfing and kitesurfing.
Masbat Bay and the Lighthouse area have narrow strips of sand between the restaurants and the water -- perfect for a quick dip between dives, but not really beach-lounging territory. For a quieter escape, head north past the Blue Hole to Ras Abu Galum, where empty beaches sit below dramatic desert cliffs and the snorkeling is superb.