Avoid the crowds found in Manly and travel on the bus 15 mins up the coast to find one of the best beaches and surf in Sydney.
Uncrowded family beach and great open air fresh water swimming pool.
Loads of restaurants and bars are on the beach front as well as what I think is the best fish and chip shop in Sydney (forget Doyles!) - you can eat them on the grass park in front of the beach underneath large trees.
Take the bus from Manly pier direct to the beach front at Dee Why - takes about 15 mins.
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There's a great walk along the ocean from Dee Why to North Curl Curl beach which has a gorgeous rockpool (i.e. open salt water swimming pool) as well. Curl Curl beach is far less developed than Dee Why or Manly.