If you fancy a swim but don't want to go too far from the city, the 1.5km beach at Katara Cultural Village is a pleasant sandy stretch with inflatable play structures for kids (purchase a day pass for QR50 from the kiosk), plus watersports from parasailing to wakeboarding on offer. Women can't swim here unless they are completely covered. Men aren't allowed to wear speedos.
Katara Beach
Doha