There is a paved walkway that hugs the water and extends from Muizenburg Beach to Kalk Bay Harbour. Along the way, you pass St. James, which features a tiny little beach, a sheltered cove, and brightly-coloured changing rooms. While parking can be a challenge (there is only on-street parking available), the beach is often uncrowded and protected from the wind by its location. Plus, the shallow, natural 'swimming pool' (built via several rock walls) makes it great for families. These boys were walking along the rock pool perimeter, periodically jumping off into the shallows and chasing small fish, and each other, around in the warm water.
Bring a picnic basket and plenty of sunscreen, and you're ready for a great beach day minus the crowds.