Who needs safety barriers? Certainly not this zoo. This is one of four or five similar primate islands (ring tailed lemur in this case) in the new AdventureLand expansion. None have any raised banks or railings around the ponds - any child (or stupid adult) could easily run into the shallow pool and onto the island.
Yes the size is good vertically, but not horizontally. Their old primate islands are all much larger, so it is surprising (translation - disappointing) they went this small on all the new ones.