snapping turtle, giant (Monster Manual)
Large Animal (aquatic)
Hit Dice: 4d8+12 (30 hp)
Initiative: +3 (-1 Dex, Improved Initiative)
Speed: 5 ft. (can’t run), swim 20 ft
AC: 16 (-1 size, -1 Dex, +8 natural)
Attacks: Bite +6 melee
Damage: Bite 1d8+6
Face/Reach: 5 ft by 5 ft. / 10 ft.
Special Attacks: Improved grab
Special Qualities: Limb retraction
Saves: Fort +7, Ref +3, Will +2
Abilities: Str 19, Dex 8, Con 16, Int 2, Wis 13, Chr 6
Skills: Hide –1*, Spot +8
Feats: Improved Initiative
Climate/Terrain: Temperate and warm aquatic
Organization: Solitary 
CR: 2
Treasure: None
Alignment: Always neutral 
Advancement: 5-9 HD (Large); 10-14 HD (Huge)
Combat
Improved grab (Ex): If a snapping turtle hits an opponent with its bite attack, it deals normal damage and starts a grapple as a free action without provoking an attack of opportunity. Each subsequent round, if its grapple check succeeds, the turtle does normal bite damage, and it is not itself considered grappled while it holds an opponent.
Limb retraction (Ex): A turtle can retract its limbs and head into its shell if damaged or threatened. This effectively gives it 100% cover, though an opponent may maneuver to be able to attack it with Large piercing weapons. Doing so may well provoke an attack of opportunity from the turtle, however. 
Skills: *A turtle has natural camouflage, giving it a +8 racial bonus to Hide in heavily weedy or swampy waters.