I suspect that most people's favourite place I know is South West Rocks, NSW Australia
Waters warm all year round, it has a big peaceful bay, with a few beaches exposed to the open sea if you like big waves.
It's a bit too commercial for me though,
Personal favourite would be Hat head, next headland down, it is as yet, pretty much undiscovered by the commercial sector, and surrounded by National park, which puts alot of red tape in the way of expansion
There's 30Km's of beach, maybe 200 people in the holiday season
Just the right place to to have lots of fun in the water, and makeout on the beach