Sydney has a very sexy side that is often hidden just out view. That next door neighbour might have a dungeon that she uses whilst her kids are at school. She might even get her husband to watch. Some places offering services like this are easy to find, whilst others opt to stay quite secretive. I am going to talk about two of the more approachable ways.
Swinging has been popular in modern culture since the 60s although the concept is prehistoric. If you feel like trying something a bit on the vanilla side, swinging is for you. There are two ways to give this a go: privately or in an on-site-sex venue.
The internet has allowed a degree of anonymity and speed that allows couples to quickly meet and introduce themselves to other like minded couples. Sites such as RedHotPie and Adult Match Maker offer this service, although there is a cost. The advantage of using sites like these to meet people is that you can take a lot of awkwardness out of the first meetings. This is sometimes a problem at a 'swingers club'.
Sydney has some well advertised swingers' clubs that generally operate across the weekends. They cater to a wide range of interests and do their best to give a luxurious service. They are often well maintained and have strict rules. This can be enforced by security if necessary, allowing everyone to have a great time with no fear of unwanted attention. A list of these can be found here.
Whilst, I understand that this type of thing is not for everyone, it exists and can be great fun if you like to explore activities outside the norm. Make sure that you do all your research and always play safe.