Cocoon

Cocoon has 11 total collectibles known as Moon Ancestors. These can be acquired as you play through the game, or easily mopped up using chapter select once you finish the story. They are most often hidden just off the main path; may involve a small and simple puzzle, and are unlocked with an interaction.
0:54 - 25% - Mariner’s Branch
Using checkpoint 25% allows this to be grabbed easily. Once you start, you can backtrack just barely to the path that brought us forward. Find a hidden path to the left, and follow the ramp to the collectible.

Relatively early in the game, you will be working with a portal that lets you place either an orange orb or a green orb into the middle and you can then jump in.

As part of the main story progression, you will first need to place the orange orb into the center and jump into the portal taking the green orb with you. This will allow you to unlock a robot companion.

Now, return back and swap the orbs around in the portal: place the green orb in the centre then jump in with the orange orb. Everything up to this point, I believe, is core progression.

Now in the green portal, head north and use the orange orb to light up the path. Whilst on this orange path, take the first left turn. This path is semi hidden by the rock and will lead to the Moon Ancestor.

(In the capture, I had already released the Moon Ancestor but this will take you to the correct location)

Check the guide below, you need to load at 24%


Timestamps:

00:00 Intro + 0-14% + Off the Beaten Path Achievement
04:49 14% - 17% + Pathfinder Achievement
06:37 17% - 24% + Mariner’s Branch Achievement
09:50 24% - 27% + Mesh Network Achievement
11:12 27% - 32% + Fundamental Changes Achievement
14:01 32% + End of the Line Achievement
14:40 32% - 46% + Skin Deep Achievement
21:45 46% - 52% + Different Destinations
26:26 52% - 56% + From There to Here Achievement
28:21 56% - 63% + Conduit Achievement
32:48 63% - 73% + This Has Potential Achievement
38:59 73% - 81% + Cryptographer Achievement
43:08 81% - 84% The Space Between the Stars Achievement
46:09 84% - 86% + A Perspective on things Achievement
47:26 86% - 90% + Daybreak Achievement
55:13 90% - 97% + Loophole Maneuvers Achievement
1:00:23 97% - 100% Cosmic Architect Achievement

CHAPTER 2 - MARINER'S BRANCH ACHIEVEMENT

You unlock this by interacting with the second Moon Ancestor in the game, you will find this in Chapter 2, this guide will take you through the second chapter, the achievement drops just around the 08:30 mark.