That's the closest thing to a "half-formed" creature that you're going to get. The mudskipper's fin that it uses to swim also doubles as a sort of leg, so that it can also move itself about on land.
The evolution of fins to limbs in the land invasion race
The website seems somewhat interesting, at first glance, with actual links to peer-reviewed papers.
I feel like I need to draw your attention to something they mention under their "Rationale" section:
"It has come to our attention that THE THIRD WAY web site is wrongly being referenced by proponents of Intelligent Design and creationist ideas as support for their arguments. We intend to make it clear that the website and scientists listed on the web site do not support or subscribe to any proposals that resort to inscrutable divine forces or supernatural intervention, whether they are called Creationism, Intelligent Design, or anything else."