We saw these Pukeko in a park in Wanganui. They were trying to eat something in the water, and were looking for a good perch.
They walked along the lilypads, which managed to hold them above the water. As soon as the birds stopped, however, they slowly started to sink. A few seconds later, the Pukeko would hop back up to the lilypads and take a few more steps before stopping, slowly sinking, and repeating the process.
While I was watching, the Pukekos never found much of what they were looking for. They were too busy being constantly surprised by their lack of buoyancy.