MEGALODON

A typical megalodon measures between 55 and 90 feet long, weighs between 10 and 60 tons, and is characterized by its streamlined body and rear-facing teeth.
A megalodon can launch itself up to 40 feet out of the water to snatch up a low-flying creature or object.
Species Traits
Improved Grab (Ex): To use this ability, the megalodon must hit an opponent at least one size category smaller than itself with its bite attack. If it gets a hold, it automatically deals bite damage each round that the hold is maintained, and it can swallow in the next round.
Keen Scent (Ex): A megalodon notices creatures by scent within a 180-foot radius. It can detect blood in the water at a range of up to 1 mile.
Swallow Whole (Ex): If a megalodon begins its turn with an opponent two or more size categories smaller than itself held in its mouth, it can attempt a new grapple check as though trying to pin the opponent. If it succeeds, it swallows its opponent, automatically dealing bite damage. Once inside the megalodon, the opponent takes bludgeoning damage equal to the megalodon's bite attack plus 1d6 points of acid damage per round from the monster's gullet. A successful grapple check allows the swallowed creature to climb out of the gullet and return to the megalodon's maw, where another successful grapple check is needed to get free. Alternatively, the swallowed creature can attack from inside the gullet using claws or a Small or Tiny slashing weapon. Dealing at least 25 points of damage to the gizzard (Defense 20) in this way creates an opening large enough to permit escape. Once a single swallowed creature exits, muscular action closes the hole; thus, another swallowed creature must cut its own way out. A Gargantuan megalodon's gullet can hold 2 Huge, 8 Large, 32 Medium-size, or 128 Small or smaller opponents.
Megalodon: CR 11; Gargantuan animal; HD 24d8+168; hp 264; Mas 24; Init +2; Spd swim 120 ft.; Defense 20, touch 8, flat-footed 18 (-4 size, +2 Dex, +12 natural); BAB +18; Grap +36; Atk +24 melee (4d6+10, bite); Full Atk +24/+19/+14/+9 melee (4d6+10, bite); FS 20 ft. by 40 ft.; Reach 10 ft.; SQ darkvision 60 ft., improved grab, keen scent, low-light vision, swallow whole; AL none; SV Fort +21, Ref +16, Will +9; AP 0; Rep +0; Str 31, Dex 15, Con 24, Int 1, Wis 12, Cha 10.
Skills: Hide -10, Listen +6, Spot +6, Swim +15.
Feats: None.
Advancement: 25-48 HD (Gargantuan); 49-72 HD (Colossal).
Advanced Megalodon: CR 17; Colossal animal; HD 49d8+441; hp 637; Mas 28; Init +2; Spd swim 120 ft.; Defense 21, touch 4, flat-footed 19 (-8 size, +2 Dex, +17 natural); BAB +43; Grap +74; Atk +58 melee (5d6+15, bite); Full Atk +58/+53/+48/+43 melee (5d6+15, bite); FS 30 ft. by 50 ft.; Reach 10 ft.; SQ darkvision 60 ft., improved grab, keen scent, low-light vision, swallow whole; AL none; SV Fort +35, Ref +16, Will +9; AP 0; Rep +0; Str 39, Dex 15, Con 28, Int 1, Wis 12, Cha 10.
Skills: Hide -10, Listen +6, Spot +6, Swim +20.
Feats: None.