The beach wasn't too skinny in March. But be warned about the rental next to Calmos can get noisy at night. Then again if you're young enough you'll be at Calmos until the music ends.

Petite Plague, the beach next to Grand Case beach club is wide. You'd pay to rent chair but perhaps they're free if you eat/drink there. Great restaurant and they will serve you on the beach if you don't want to leave your chair.