One of my best favourite walk routes in sydney is from manly to shelly beach. It has a beautiful view overlooking the blue ocean water. Taking a train from city area to circular quay then a 30 min ride by ferry to manly suburb, is very recommended, albeit it is a bit pricey compared to a bus ride.
As you go in and the ferry goes by; imagine you are sitting on the outside deck, and the wind breeze, refreshing indeed. You could close your eyes and relax your mind or simply just enjoying the vantage view of sydney city.
✨Recommended things to do in manly area: snorkeling/swimming at shelly beach, surfing at manly, visit boathouse for a quick snack at shelly beach, visit papi chulo restaurant at manly wharf for bbq platter.