n small amphibious mindless ooze 

Perception +4; motion sense 60 feet, no vision

Skills Athletics +6, Stealth +3

Str +3 Dex -2 Con +2 Int -5 Wis +0 Cha -5

Motion Sense An amoeba swarm can sense nearby creatures through vibration and air or water movement.

AC  8; Fort +7, Ref +3, Will +5

HP 45; Immunities acid, mental, precision, critical hits, unconscious, visual

Speed 10 feet, climb 10 feet, swim 10 feet

Melee [>] pseudopod +8, Damage 1d6 acid plus Grab

Constrict [>] 1d4 bludgeoning plus 1d4 acid, DC 17

Envelop [>>>] Requirements The giant amoeba begins its turn with a target its size or smaller grabbed; Effect The giant amoeba maintains the Grab and extends pseudopods to surround the creature and pull it inside the amoeba's body. This thereafter has the same effect as if the amoeba had Engulfed the creature (DC 17, 1d6 acid, Escape DC 17, Rupture 3).

Weak Acid An amoeba's acid damages only organic material—not metal, stone, or other inorganic substances.

Bestiary 2, page 192.