If hunters chase an animal into the water while throwing spears at it, it sometimes turns red injury in mid-stream. It doesn't drop dead until it reaches the other shore. But when it is butchered, the meat falls into the water in which the hindquarters of the animal was submerged. This meat cannot be picked up. I had three children standing in the stream, flashing that they were going to get raw meat, until they either gave up or in one case sat down in the water and ate a piece of it. I pitched that village and learned not to chase prey into the water, but the animals are programmed to run for the water when chased, at least the ones that don't race off the map, so my hunters are not getting much prey now.

Could the prey animal maybe walk completely onto the land before flopping over dead, so the butchered meat doesn't land in the water?

I did not keep it. Sorry. If it happens again I will make a special save and send it to you.