I haven't often had a good view of a Blue-billed Duck. Dr Harry Frith wrote that it is usually believed to be a rare species but that this is entirely due to its secretive habits and dense habitat.*
Luckily, we found three males in a couple of the small lakes at Karkarook Park and got good views when they swam out from the cover of the swamp vegetation along the edge.
*Frith, H.J. (1967). Waterfowl in Australia. Angus and Robertson, p.305.