At about 15km from Devonport, we were there in no time at all.  What a charming little town, full of antique stores and little cafes.  We stopped at Reliquaire, a shop with lots of beautiful dolls, antiques, ice cream, coffee, bric-a-brac, and most important of all, a platypus viewing map.  We looked around the store, and with map in hand, left to find a creek just 5km out of town down Shale Road.  As we drove along the Mersey River, we passed the Henry Somerset Conservation Reserve, a perfect campground if ever there was one—but alas, with no camping allowed.  Further on was Warrawee Forest Reserve, another idyllic spot where camping was prohibited.  It did, however, have a pond with a “Platypus Walkway”.  This was known as a good place to find platypus.  It was a lovely picnic area along the river, and as we waited for late afternoon, we sat and watched a number of Superb Blue Wrens darting about the picnic grounds. 
Eventually we made our way over to the platypus boardwalk, and were rewarded with a view of one of these remarkable monotremes (one of only two egg-laying mammals in the world) floating along on the surface of the water.  It dove down a few times in search of food, then soon vanished into a bed of water reeds.  Other good viewing areas for platypus were under the bridge in Latrobe, and behind the police station.  We would have spent the night in Latrobe, but with no camping facilities (only a few comfortable-looking hotels), we decided to move on to Sheffield where we spent the night in the local caravan park.