My first attempts (shown here) at a duckling were good at imitating but poor at casting due to a strong wind resistance.
I slimmed the foam in the new version down similar to the Morrish Mouse and this cut back the wind resistance. The first is tied on an Ad Swier #8/0 Pike hook, my second version is tied on a 55mm articulated shank (self made) with a #2 double tube fly hook attached. This rides nearly weedless behind the deer hair. I eliminated the bucktail beak to cut down on spinning, also a few coats of Exterior Delta Ceramcoat were added to strengthen the foam.
With the Muskrats I simply coated the foam with Furry Foam and used beaver instead of deer hair for a nearly indestuctable body. There is a little more weight here when it is wet that helps reduce the wind resistance. It is tied on a #8/0 Ad Swier Pike hook, I want to make some more with the articulated shanks and tie the tail on the hook itself to keep from tangling.
If the weather is good in the next few days I'll make some videos of them swimming from above and below the water surface.