I stood in roughly this same spot about two weeks ago and watched 400 hippos jostling for space in the shallow water. In the space of a few days, they’ve all moved out.

Add 20 cms to the river depth, which is what the rain in surrounding areas has done, and it becomes uncomfortably deep for a resting hippos. The small amount of rain locally will also have re-filled some of the nearby lagoons, which the hippos prefer to the faster-flowing river.