Under an hour from the centre of Sydney is Scotland Island, a lovely little island in Pittwater.
To get there, you must drive and park at Church Point wharf (head to Mona Vale on Sydney's northern beaches then follow the signs towards Bayview and Church Point).
Check the ferry times here by the wharf, there is one each hour. On weekends they leave at half past the hour. While you wait you can grab a coffee or snack at the scenic store / café overlooking the water.
Then time to hop aboard! Dogs are welcome too. There are four ferry stops on the island: Bell Wharf (5 minutes across the water), Carols Wharf, Eastern Wharf and Tennis Court Wharf (10 minutes on the ferry). Tennis has a park, community centre and BBQ facilities (but no toilet) so we decided to get off here, and this way we circumnavigated the island on the way, checking out some of the great houses by the sea, most of them quite cheap for Sydney prices.
My map (from the ferry) tells me there is a house here that was owned by the infamous madam Tilly Devine in the 1920s. Had we stayed to be picked up at Tennis, we could have then watched the ferry stop at the national park spots Lovett Bay and Elvina Bay for the 15 minute trip back. Unfortunately the park was completely underwater the day we arrived (it had been raining quite a bit).
So we hot-footed it across the island to catch the ferry back from Bell wharf (there are more ferries returning from Bell than the others). It's interesting to see how the locals live, with rain tanks in each backyard, various watercraft strewn about and all sorts of odd transportation devices like golf carts and dirt bikes. However we hadn't realised just how steep the hills were. Piggybacking a 4 year old up steep hills with a scooter in tow (best to leave the scooter behind), and hoping to make the ferry was a little stressful.
We did miss the ferry but managed to pass the time by playing on the jetty. Little had we realised we were at the wrong ferry stop and the following ferry was just a "mail run" that skipped us completely.
If you arrive at this wharf you could be waiting some time...
It wasn't until hours later when the driver of the school ferry heading to Newport stopped and explained we should be at Bell Wharf. We hadn't realised where we were as the only wharf sign faces the boats at sea, not visitors coming from inland. Together with another couple who had made the same mistake we ran back up the steep incline, along the muddy road and down the hill in pouring rain, where we finally caught the ferry home after spending many more hours than we intended to on the island.
I would recommend Scotland Island on a sunny day where you could have a lovely BBQ at Tennis Wharf, bush walking up to the lookout and then back down to your original spot, so at least you would be assured the ferry will come when you expect it.
Every Christmas Eve the Scotland Island dog race is held, where the dogs of the island have a race to see who makes it across first. Entrance fee is a can of dog food and a beer. The winner takes all.