After promising myself I wouldn't, and then running into a bit of trouble with a population of 17 and not enough food to go around, I read the puzzle solutions for how to get rid of the sharks (I assume that lets villagers start fishing?)

Anyway. How is the potion found? Is it through random experimentation, or is there an event? I don't want to completely cheat by just following the guide if I may be given an event to save my poor lil guys!

Thanks in advance to anyone who knows the answer to this

You have to have the right level in your chosen faction first, but after that you can find it through experimentation with potions. Have you solved Puzzle 7? You'll find something there to help you.