I think there may have been three hippos from memory, but the activity in the water to the left of the hippos is actually caused by African catfish, of which the pool is full. The reason there is so much splashing is because a keeper was over there throwing bread in (for the fish,not for the hippos).
The pool is huge compared to what is often seen in hippo enclosures, but there isn't really a lot of land unfortunately.
