If you've never been to Kangaroo Island, shame on you. There really is no excuse for not exploring this place of natural wonder.
Sealink are offering a discount on the 7pm ferry service between Cape Jervis and Penneshaw, and also 7.30pm ferry service from Penneshaw and Cape Jervis until March 2012 for just $19.90 one-way.
Twilight ferry fare is also available on the 6pm ferry from Cape Jervis during 23/7/2011 - 25/9/2011)
So, why waste a night sleeping on the mainland or in a B&B when you could be at sea. You can catch a Friday ferry, spend two days exploring with a little extra cash to upgrade your Saturday night accommodation and then return on Sunday night arriving on Monday morning.
Sealink Ferries are not the Queen Mary, so you'll need to think about some warm sleeping gear and have your sea legs. Think of it as camping at sea, get up in the night and stare at the immense star filled sky.