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..)