Legs and flippers are modeled as a separate object. Create splines according to the picture below. Create four circles, attach them together and modify them according to the picture. Use exactly the same number of vertices.
Create a new spline to the side of the leg according to the picture below.
Add a new spline into the leg according to the picture below.
Finalize the leg by creating two new splines according to the picture below.
The complete leg should look like in the picture below. I think the leg is rather easy and fast to model with splines.
Create materials and the duck is complete. It could look like in the picture below. The picture below was rendered by using Skylight and enabling Final Gather in Mental Ray.
Animating the Duck
The duck should deform smoothly when animated because it mostly consist of quads (four sided polygons).