Light-to-Light, Ben Boyd NP
The Light-to-Light walk in Ben Boyd National Park just south of Eden NSW is an easy three day walk south along the coast to Green Cape. I did it as a six day return walk, which gave me an excuse to stay in the bunkhouse at Green Cape, avoided having to organise transport back from Green Cape, and amortised all the costs and organisational overheads over six days instead of three.
The entire walk from north to south could be done as a two day walk, but what's the rush? By taking three days you avoid having to camp at the drive-in paid campsites and have more time for swimming, taking photos, birdwatching or whatever.
I did it in April and the ocean temperature was easily warm enough for swimming, although that will probably vary from year to year. There's a great little beach at Mowarry Point.
While you can camp at the paid campgrounds at Saltwater Creek and Bittangabee, they are reasonably expensive for what they provide for bushwalkers, can be busy and are aimed at car campers. You're better off camping at the walk-in campsites at Mowarry Point and Hegartys Bay. There are small creeks at both of those free campsites but they may dry up in summer or after long dry periods. Check with the Merimbula National Parks and Wildlife Service office on current conditions just before you start the walk. Walk with enough water to get you to the next paid campground just in case the creeks are dry and you have to continue on.