Both in Survival and Creative, animals get stuck in deep water.
Easiest way to reproduce
In Creative:
Start new world
Go near the shore
Spawn lots of sheep or cows onshore
Fly up and watch
Naturally lots of the animals end up in the water. But some of them get stuck in the same position. They can turn, and bob, but don't seem to move.
Sometimes by knocking the animal, it starts moving, and can swim around.
In Survival:
Start new world
Run around until you find some animals near the shore
Climb up into a tree and watch.
Same here. Some animals get stuck in the same position. They can turn, and bob, but don't seem to move.
This issue is a duplicate of MCPE-992, but that issue has not been updated with affected version since 0.6.1. Please update MCPE-992 before you close this issue.
(I tested on Xperia Z, but according to the comments in MCPE-992, it is not device dependant..)
By the way, MCPE-992 is the highest voted PE issue.
Please please please fix....
It's a bit silly herding your sheep with a snorkel instead of a crook