Visit Peterson's Creek in Yungaburra.
Early morning or late afternoon are probably the best times but they have been seen throughout the day. There is a viewing area near the road but if you have time, explore along the creek. Before you start drop into the Yungaburra Visitor Centre for a map and an update on recent sightings plus some good old commonsense advice. Have a great time exploring and photographing.
WHERE CAN I SEE A PLATYPUS
Australian Platypus Park at Tarzali Lakes is another option. If you are in the Millaa Millaa area the address is 912 Malanda - Millaa Millaa Road. Great food, great coffee and of course great Platypus. Guided tours are provided to the Platypus viewing area at a fee of $7
or less if in a group. Well worth a visit. If you intend platypus spotting I suggest you search out local knowledge. In this case phone the Australian Platypus Park (07) 4097 2713. I understand the best months for platypus spotting is from March to November.