Start Chapter 12: Skipping Stones
Play normally until Chapter 12 begins, or load it directly from Chapter Select if you are cleaning up after missing the achievement. The objective happens during the skipping stones minigame, not during a later chapter.
Reach the stone-throwing minigame
Continue until the game lets you aim and throw stones across the lake. You can still enjoy the scene naturally, but if you want the achievement, shift your attention to the right side of the water instead of only skipping across the open lake.
Find the tyre swing on the right
The target is the tyre swing hanging on the right side of the lake. Players often miss the achievement because the minigame feels like it is about skipping stones for distance or style, but the hidden target is the tyre.
Aim at the upper center of the hole
The stone goes where the small aim dot is placed, so line the dot up with the top-middle or upper center of the tyre opening. Aiming too low can clip the lower edge or fall short, while aiming too far to the side can miss the opening entirely.
Charge the throw and release
Hold the throw input to build enough power, then release. If the stone misses, adjust slightly and try again. You can keep attempting the throw during this minigame, which makes Skim Gordon more forgiving than achievements with one-shot routes.
Do not leave until the achievement unlocks
After the characters finish talking, the game may let you leave the minigame. Do not use the leave prompt until you have successfully thrown through the tyre and seen the unlock. Leaving early is the easiest way to turn a quick achievement into a Chapter Select replay.