Once you leave the Siwa region to travel to Alexandria at the end of the Prologue, start travelling toward the quest marker.
When you are approximately 1500m away, and just South-West of Sais on your map, there is a hippo lair. Simply shoot an arrow, run away, wait for the game to give you the visual indication you are out of combat, rinse and repeat. Should take you only a couple of minutes.
Let's keep cheevin' together!