Alexandria Bay, on the far eastern side of Noosa headland, is a long, broad, wild beach reached only by a forty-minute walk through the national park. It feels nothing like the manicured, sheltered Main Beach back in town — the swell rolls in hard, the sand stretches uninterrupted for over a kilometre, and on most weekdays you might share the whole beach with a handful of other people.
The bay has long been Noosa's unofficial clothing-optional beach; it is not posted as such, but the dress code (or lack of one) is well established. The surf is too unpredictable for casual swimmers, but it makes a wonderful walk-end picnic spot. Carry water and check the tide before you go.