n large animal 

Perception +11; low-light vision, scent (imprecise) 30 feet

Skills Athletics +13, Stealth +11 (+13 in water), Survival +11

Str +6 Dex +2 Con +6 Int -4 Wis +4 Cha -2

Deep Breath The hippopotamus can hold its breath for 5 minutes.

AC  21; Fort +15, Ref +9, Will +11

HP 85

Speed 25 feet, swim 20 feet

Melee [>] jaws +15 (deadly d10), Damage 2d8+8 piercing

Melee [>] foot +13, Damage 1d10+8 bludgeoning

Aquatic Ambush [>] 30 feet

Capsize [>] (attack) The hippopotamus tries to capsize an adjacent aquatic vessel of its size or smaller. The hippopotamus must succeed at an Athletics check with a DC of 25 (reduced by 5 for each size smaller the vessel is than the hippo) or the pilot's Lore DC, whichever is higher.

Trample [>>>] Medium or smaller, foot, DC 23

Bestiary 2, page 144.