Being at the bottom end of the Miramar peninsula, you can get there by bus. Its big advantage is the shelter it offers from the prevailing north westerly! There is a car park at the access point to the beach, at the south end of the 'Pass of Branda' in the suburb of Seatoun. The area of the beach commonly used is from the 'hole in the rock' (about 100 m from the car park) out to the point. At the height of summer, clothes aren't needed until well after 8 pm - and some spectacular sunsets can be seen from here.
Peka Peka is really the first beach north of Wellington on the Kapiti Coast where skinny-dipping is not only 'known to occur' thus: legally safe; there is also a sign to acknowledge it. The most commonly used area these days is north Peka Peka Beach, accessed from the end of Te Hapua Rd, 5 km north of Waikanae. (Although there have been occasional reports of skinny-dippers seen at Queen Elizabeth Park, near Paekakariki, about 20 km south.)
This area is about 10 km inland from Waikanae, off the Akatarawa road. It is a DoC reserve. This spot is just downstream from the car park, in the opposite direction to the walking track to Otaki Forks.