Mobs become invisible after travelling in boats

After I entered a boat, I noticed i had a chicken in the boat with me. After reaching my destination, I broke the boat to get it back, to discover floating particles where I expected to chicken to be. The chicken appeared to be invunerable (from what I could tell) as well as being invisible apart from the particle effects. Not exactly gamebreaking, but it's still a small bug with the new boats, so I thought I'd mention it.