Dire Shark (CR 9)

Huge Animal (Aquatic)
Alignment: Always neutral
Initiative: +2 (Dex); Senses: keen scent, Listen +12, and Spot +11

AC: 17 (-2 size, +2 Dex, +7 natural), touch 10, flat-footed 15
Hit Dice: 18d8+66 (147 hp)
Fort +14, Ref +13, Will +12
Speed: Swim 60 ft.
Space: 15 ft./10 ft.
Base Attack +13; Grapple +27
Attack: Bite +18 melee
Full Attack: Bite +18 melee
Damage: Bite 2d8+9
Special Attacks/Actions: Improved grab, swallow whole
Abilities: Str 23, Dex 15, Con 17, Int 1, Wis 12, Cha 10
Special Qualities:
Feats: Improved Natural Attack (bite); Toughness (4); Weapon Focus (bite)
Skills: Listen +12, Spot +11, and Swim +14
Advancement: 19-32 HD (Huge); 33-54 HD (Gargantuan)
Climate/Terrain: Cold aquatic
Organization: Solitary or school (2-5)
Treasure/Possessions: none

Source: Monster Manual

Improved Grab (Ex): To use this ability the dire shark must hit with its bite attack. If it gets a hold, it can try to swallow the foe.

Swallow Whole (Ex): A dire shark can try to swallow a grabbed opponent of Large or smaller size by making a successful grapple check. Once inside, the opponent takes 2d6+6 points of crushing damage plus 1d8+4 points of acid damage per round from the shark's digestive juices. A swallowed creature can cut its way out using claws or a light slashing weapon by dealing 25 points of damage to the shark's digestive tract (AC 20). Once the creature exits, muscular action closes the hole; another swallowed opponent must cut its own way out.

The shark's gullet can hold two Large, four Small, eight Tiny, sixteen Diminutive, or thirty-two Fine or smaller opponents.

Keen Scent (Ex): A dire shark can notice creatures by scent in a 180-foot radius and detect blood in the water at ranges of up to a mile.

Dire sharks attack anything they perceive to be edible, even larger creatures. They bite with their powerful jaws, swallowing smaller creatures in one gulp.

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.