The spit bridge to manly walk is a great free way to experience Sydney harbour, discover numerous beaches and see some amazing wildlife. Personally I enjoy completing the walk from the spit bridge to manly (not manly to the spit bridge). This way you can explore manly when you’re finished and there are more transport options.
The walk is approx. 10km and can take anywhere between 1 - 4 hours to complete. The walk can be challenging in some areas however it is suitable for kids. It is possible to complete the second half of the walk in a wheel chair or on bikes. (North harbour to Manly).
There are plenty of bathroom facilities and water stations along the way. I suggest bringing your swimming gear and having a swim at one of the many beaches along the walk. (Don't forget your camera).