Twice we experienced that the animals we wanted to see were under water.
The first was a crocodile in a pond at Matswani. They had placed two crocodiles in a pond, but one had disappeared. They had no idea how. When we camet o the pond the animal was on the shore, but jumped immediately in the water. It was curious so we saw the eyes close to where we were sitting.
We visited a large national park to see more animals. They had a hippo in a pond and a deck partially over the pond for visitors like us. The hippo must have been shy as it was hiding under the deck with only its head sticking out. But that was under water so again was part of the head all we could see.