From Pathfinder Society Intro #1: The Second Confirmation, which isn't enabled.

Swampy Quicksand

COMPLEX HAZARD 2

Stealth +10 (trained), or DC 0 and no minimum proficiency if the surface is disturbed.

Description A 15-foot-wide patch of water and sand attempts to submerge creatures that step onto it.

Disable DC 16 Survival (trained) to disturb the surface

Submerge

Trigger A Huge or smaller creature walks onto the quicksand

Effect The triggering creature sinks into the quicksand up to its waist. The quicksand rolls initiative if it hasn't already.

Routine

(1 action) On its initiative, the quicksand pulls down each creature within it. A creature that was submerged up to its waist becomes submerged up to its neck, and a creature that was submerged up to its neck is pulled under and has to hold its breath to avoid suffocation.

A creature in the quicksand can attempt a DC 18 Athletics check to Swim to either raise itself by one step if it's submerged to its neck or worse, or to move 5 feet if it's submerged only up to its waist. On a critical failure, the creature is pulled down one step. A creature that Swims out of the quicksand escapes the hazard and is prone in a space adjacent to the quicksand patch. Other creatures can Aid the creature, typically by using a rope or similar aid, or attempt to pull the creature out with their own DC 18 Athletics check, with the same results as if the creature attempted the check.

Reset The hazard still submerges anyone who walks in, but the surface doesn't become hidden again until it settles over the course of 24 hours.

Pathfinder Society Intro #1: The Second ConfirmationOGL