Zaratan
XP: 307,200
N Colossal animal
Init +4; Senses low-light vision; Perception +26
DEFENSE
AC 37, touch 6, flat-footed 33 (+4 Dex, +31 natural, -8 size)
HP 192 (11d8+143)
Fort +18, Ref +7, Will +7
DR 20/magic; SR 20
OFFENSE
Speed 5 ft., swim 20 ft.
Melee bite +21 (4d6+31/19-20)
Space 30 ft., Reach 25 ft.
Special Attacks Reflex anything on the water in-fount of the mouth may be swallowed whole.
STATISTICS
Str 52, Dex 19, Con 36, Int 14, Wis 23, Cha 21
Base Atk +8; CMB +37; CMD 51 (55 vs. trip)
Feats Critical Focus, Endurance, Great Fortitude, Improved Critical (Bite), Improved Great Fortitude, Power Attack
Skills Perception +26
Racial Modifiers -4 Perception for sound-based checks
SQ buoyant, shell, slow and steady
ECOLOGY
Environment temperate ocean
Organization solitary
Treasure G.M. Discretion
SPECIAL ABILITIES
Buoyant (Ex) A zaratan that fails a Swim check by 5 or more does not sink.
Shell (Ex) As a move action, a zaratan can pull its extremities and head into its shell. It can't move or attack as long as it remains in this state, but its armor bonus from natural armor increases by 4 as long as it does. It may end this state as a move action.
Slow and Steady (Ex) A zaratan's speed is never modified by armor or encumbrance.
A massive Creature that never stops growing at birth they have a shell that is 75 ft by 150 ft. the Largest known Zaratan had a shell measuring over 500 ft by 750 ft.
They have been known to eat whole ships with out waking up. the stomach of such a beast in thought to hold massive treasure.
An animal with Int14 is a bit odd. Wis23 Cha21 is just crazy. Why?
As he is, I'd say he's CR...10? Just a wild guess. He's tough and strong, but has very few ways to threaten anything.
Really though, this kind of monster is where Pathfinder rules utterly fail. This guy's bite wouldn't hurt you; his mouth is so big, he'd just swallow you whole every time. It'd be like me trying to crush a bacteria between my molars.
And to think that anything short of a meteor is going to harm such a creature is just as silly.
An encounter with something like this shouldn't be a combat. At least, not one run in the traditional way. Make him even bigger and make him an environment.