Heading out past the new Woollies (pick up some supplies on the way?) you cross the Princes Highway and ride through the park, along Marsh St for a bit and under the motorway. Once you find the marked, smooth, completely separated cycleway, you just need to follow your nose the entire - and mostly flat - 20km to Cronulla.
Well, a map might help so perhaps visit Bikely before you set off.
Basically once you've found the bike path and you pop out at Kyeemagh (and are finished gawking at the still-operational market gardens) the ride follows the water the whole way around Botany Bay. It might have an industrial backdrop with a large international airport as the soundtrack but on some days the water is crystal clear and all you can see is a white sand beach the length of the bay.
The beauty of this ride is it finishes in Cronulla where you can stuff yourself with fish and chips and ice cream before making the biggest decision of the day... To ride back where you came from, or hop on the train back home. With a tummy full of chips and tartare sauce I dare say you will opt for option #2 while promising yourself you'll try the return trip one day "when I'm more fit".
