The annual migration is beyond our imagination, thousands of wildebeest and zebra follow the greening grass from Tanzania into Kenya's Masai Mara. The last barrier in their journey is the Mara River. Hundreds will gather on the far bank, waiting & watching until a few brave the drop and swim. The crossing may start and turn into a flood of beasts jumping, running, and swimming as fast as they can â€“ or the entire herd may stop, turn and retreat, only to approach and try the crossing at another time. Waiting are the crocodiles.