Wedged between the ancient Daintree rainforest and the world famous Great Barrier Reef, Cairns is at the very top of any nature lover's bucket list.  The dense inland greenery hides a wealth of wildlife and waterfalls while the warm, crystal blue waters of the Coral Sea contain an abundance of marine life.  Whether it's a gap year before university, a mid-career sabbatical, or a life-changing retirement, here are some ideas to help you tick off your lifelong to-do list.