How do I recapture a domesticated penguin?

Ok. Today is just one of those days. I caught a penguin in a domesticrate, accidentally released it into the water. Went back a few days later. it was just swimming in the water. I managed to get it to follow me back up onto the little island where I caught it by whistling.

I cant seem to catch it in an iron cage or a domesticrate again. I built a fence, but every tine I enclosed it in the fence, it slides out by some unseen force.

No idea how I can get it back to my camp.

any ideas? thank you.