This large pond forms part of the park's biodiversity garden - which itself is host do dozens of indigenous plant species. Right alongside the garden area are benches and large open grassy areas where you're welcome to lay open your blanked and unpack your picnic basket. The trees are unfortunately not yet large enough to provide lots of shade, so I'd probably advise an early morning or evening picnic - outside of core sunburn hours. :)
The park is right next to the Green Point stadium, very close to the Green Point lighthouse. Entrance is free and the gates are open every day from 07h00 until 19h00.