Never underestimate how wild Tasmania is. Although the wilderness is easy to access, once you are out there, you are really out there. Which is what is so wonderful about it. But you need to take care. Always tell someone where you are going, try not to hike alone, sign the national park log books and have an emergency kit with you. As well as the obvious map, compass and plenty of water. Plus purification tablets. And be well packed with layers and waterproofs.
Always check what swimming conditions are and swim in designated zones. The currents can be fierce in Tasmania, so stick to what the experts know. Popular beaches will have lifeguards in summer. For example, the rips on the Three Capes can be huge. There are places you can swim but you need to seek local advice. One of the best places for swimming is Flinders Island which is fantastic for children. And the water is cold, more like the UK than Australia, so be prepared.
Take care driving on mountain roads not only for bends, but also ice and, of course, wildlife. It is often swerving to avoid an animal that can cause an accident, so go slow and be prepared to stop. Dawn and dusk are when you see most animals.