Baby cows, sheep, and pigs will not attempt to stay afloat in bodies of water deeper than two blocks, and they will eventually drown.
Tested in Survival and Creative
To Reproduce:
Push/spawn/lure a baby animal into a body of water deeper than 2 blocks.
Duplicate of MC-9388, please use the search function to see if your bug has already been submitted. Currently over 55% of tickets are being closed as duplicate.