Little Bay Beach is a gorgeous little spot, still not very well known. It's the last sand beach…read morebefore Botany Bay. Because it's a sheltered cove, there isn't any surf, but the place is great for paddling and snorkeling. Don't be put off by its proximity to Long Bay Gaol, or by its proximity to Malabar sewage treatment -- they've got that stuff all sorted out now, right?
Little Bay Beach has wonderful sandstone outcrops, perfect for having a picnic with friends, and a nice mix of sun and shade. The abundance of little outcrops and cave-like spaces means you often find canoodling couples in various states of undress, spread out on towels and picnic blankets, with grapes, hummus and watermelon strewn about ... it gives the whole place a relaxed, bacchanalian sort of feel.
There was an old hospital in Little Bay (long since closed down), which used to make the entrance to the beach quite creepy. In recent times they've built a housing subdivision at the old Prince Henry Hospital site, so the place isn't quite so spooky or derelict, but the development isn't too close to the foreshore, so you can't see buildings when you're sitting at the beach. It was quite a creepy hospital: used during the Bubonic plague in 1900. There are still a few heritage hospital buildings around, otherwise the rest of the structures are very new.
There is a golf course nearby, but the risks of getting hit on the head by a golf ball are probably lower than your average Sydney bluebottle sting risks, so I reckon it's worth it.
Little Bay achieved art-world fame back in 1969, when Christo wrapped it up in fabric. The whole bay. There are some great photos of it here: http://kaldorartprojects.org.au/project-archive/christo-and-jeanne-claude-1969
Little Bay's remoteness means that you can still find a park, if you drive there. But it is also accessible by bus. Just go down Anzac Parade, almost forever...
The best bit? Feels like a holiday retreat, but it's in Sydney.
The worst bit? No waves. Flat as a tack.