I've been stung by a bloody blue bottle at the beach. A form of jellyfish that sting like a bee but not deadly. One sting in 37 years. If you see them on the shore it is best to avoid a swim and have a perve, instead.
Foreigners are told about funnelweb spiders and there are some in and around Sydney here and there. However, I have never seen one except in a zoo. Ditto for snakes. I saw one on the road up in Byron Bay several years ago. I finally saw a small marsupial near Mount Wilson near Sydney. Otherwise, you seldom see any Kangaroos or Koalas unless you go to zoos or way outback.
Since you hear about sharks you do wonder about them when you go for a swim. I recall my first swim at Bondi in 1969. I got a bit concerned at every shadow I saw but they were just seaweed! If the sharks wanted to feed on humans no one would be safe. Most attacks happen when guys are spear fishing or riding boards and sharks mistake them for something else. No one has been taken by a shark at a patrolled beach in Sydney since the 1930s and in that instance the guy was spearfishing.
The beaches in Sydney are fabulous and there are at least 15 big beaches with fine sand. The beaches extend from the south way up the east coast to Cairns. Americans and Canadians are always impressed by what they find here. Too bad the locals cover their breasts now. About 15 years ago about 1/4 of women on some beaches went topless. Sydney has a couple of nudist beaches, too. So, if you like the water this is a great country to live in. There is no real winter in Sydney and there are flowers blooming every month of the year. The climate here is similar to northern Florida. Brisbane is on the same latitude as Miami. You can drive towards the equator north of Brisbane for another 1500 miles. This is a huge country.
No matter how long foreigners live here they aren't considered Aussies. I am an Australian citizen but don't think of myself as an Aussie. No matter, the Sheilas here love foreign accents. No wonder the local males hate Yanks, etc. Seems to be a lot of resentment for guys who spend a lot of money on women on days such as Valentine's Day. It is slowly catching on over here.
The Asians are impacting on Australia and I would bet that they will own the majority of businesses in the not too distant future. They shouldn't let Asians teach other Asians how to drive, though. That shows how the Aussies still view immigrants according to races and origins.
All in all it is a great place to live if you can afford it! It is expensive to travel to Europe or America and that is a bummer. Also the holidays here occur when it is winter in the Northern Hemisphere.
Sydney has about 4 million people and is one huge city. Traffic is heavy a lot of the time so it takes a lot of time to get around. The Gold Coast south of Brisbane is a rapidly growing area. And so it should be because it has beaches and mountains and subtropical vegetation and climate.