From Pathfinder Society Scenario #4-99: Blessings of the Forest, which isn't enabled.

Hidden Forest Bog (5-6)

COMPLEX HAZARD 6

Stealth +18 (expert)

Description A 15-foot wide area of verdant-covered water attempts to suck creatures down into it.

Disable Two DC 25 Survival (trained) checks to find roots and tree limbs sturdy enough for everyone to use as escape paths ends the hazard's threat to all creatures in the area

Heavy Water

Trigger A creature enters the area of the bog.

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

Routine

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

A creature partially or fully submerged in the bog can attempt a DC 23 Athletics check to Swim to either raise itself by one step (pulled under to submerged to its neck, or submerged to its neck to submerged to its waist), or to escape from the bog if it's submerged only up to its waist. This DC increases to DC 25 Athletics for creatures submerged up to their neck or worse. On a critical failure, the creature is pulled down one step. Other creatures can Aid, typically by using a rope or similar assistance (providing an automatic success), or attempt to pull a single affected creature out with their own Athletics check, with the same results as if the aiding creature attempted the check itself.

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

Pathfinder Society Scenario #4-99: Blessings of the ForestOGL