Megalodon (CR 11)

Gargantuan Animal (Aquatic)
Alignment: Always neutral
Initiative: +2 (Dex); Senses: darkvision 60 ft., keen scent, low-light vision, Listen +10, and Spot +10

AC: 20 (-4 size, +2 Dex, +12 natural), touch 8, flat-footed 18
Hit Dice: 24d8+189 (297 hp)
Fort +21, Ref +16, Will +9
Speed: Swim 120 ft.
Space: 20 ft./10 ft.
Base Attack +18; Grapple +40
Attack: Bite +25 melee
Full Attack: Bite +25 melee
Damage: Bite 4d6+15
Special Attacks/Actions: Improved grab, swallow whole
Abilities: Str 31, Dex 15, Con 24, Int 1, Wis 12, Cha 10
Special Qualities:
Feats: Improved Critical (bite); Toughness x7; Weapon Focus (bite)
Skills: Listen +10, Spot +10, and Swim +27
Advancement: 25-48 HD (Gargantuan); 49-72 (Colossal)
Climate/Terrain: Any aquatic
Organization: Solitary or swarm (5-20)
Treasure/Possessions: None

Source: Monster Manual II

Improved Grab (Ex): If a megalodon hits an opponent that is at least one size category smaller than itself with a bite attack, it deals normal damage and attempts to start a grapple as a free action without provoking an attack of opportunity (grapple bonus +40). If it gets a hold, it can try to swallow on the next round. Alternatively, the megalodon has the option to conduct the grapple normally, or simply use its jaws to hold the opponent (-20 penalty on grapple check, but the megalodon is not considered grappled). In either case, each successful grapple check it makes during successive rounds automatically deals bite damage.

Swallow Whole (Ex): A megalodon can swallow a single creature that is at least one size category smaller than itself by making a successful grapple check (grapple bonus +40), provided it already has that opponent in its mouth (see Improved Grab, above). Once inside the megalodon, the opponent takes 2d8+10 points of bludgeoning damage plus 1d8+4 points of acid damage per round from the megalodon's gullet. A successful grapple check allows the swallowed creature to climb out of the gullet and return to the monster's maw, where another successful grapple check is needed to get free. Alternatively, a swallowed creature can try to cut its way out with either claws or a light piercing or slashing weapon. Dealing at least 25 points of damage to the gullet (AC 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 opponent 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.

Keen Scent (Ex): A megalodon notices creatures by scent within a 180-foot radius and detects blood in the water at a range of up to one mile.

Megalodons attack anything they perceive to be edible - including each other. They can leap as high as 40 feet out of the water to snap at low-flying rocs and small dragons. They bite with their powerful jaws and can swallow smaller creatures.

Aquatic Subtype

Creatures with the aquatic subtype always have swim speeds and thus can move in water without making Swim checks. An aquatic creature can breathe underwater. It cannot also breathe air unless it has the amphibious special quality.