Giudeu is the most famous and popular beach in Chia; it's the one with the small island and the beautiful dunes. To tell the truth, there are dunes in other beaches but no quite as spectacular. Be careful because they're protected and climbing on them is prohibited. You shouldn't have any trouble as the dunes are cordoned off and there are plenty of signs asking you to stay off. The sand at Giudeu is fine and golden and the sea is a nice shade of blue-green that stays shallow for many feet. It's ideal for children, but also for those who only want a relaxing dip in the shallows. More athletic types will have to go quite a bit further out to reach deep water.