Stranded Deep

Just need to get to day 20. Even if you die and reload it will pop. Just be careful not to save if you are near death or have a negative effect such as poisoning as pipi can be really hard to find.

This should unlock naturally on your way to completing the rest of the achievements.

For those wanting to do this quick, please note it takes roughly 12 hours of idling. 9-10 hours if you sleep every night.

To wait out time. Just make sure you are on creative mode and just stand on an island.