Parrots disappear when entering the back of a boat

I put a lead on my horse and put one on my Parrot, I got in my boat to get across the ocean, my lead on the horse broke so I took the lead off my Parrot so he wouldn't get pull under water, I go get the lead under water, I put the lead on the horse but the Parrot get stuck into the back of the boat, so I just go with it and get in the boat and the Parrot disappeared and I haven't seen it ever since.