Liopleurodon (CR 15)

Colossal Animal
Alignment: Always neutral
Initiative: +0; Senses: keen scent, low light vision, and Spot +44

AC: 22 (-8 size, +20 natural), touch 2, flat-footed 22
Hit Dice: 38d8+456 (627 hp)
Fort +33, Ref +21, Will +15
Speed: Swim 90 ft.
Space: 30 ft./20 ft.
Base Attack +28; Grapple +62
Attack: Bite +38 melee
Full Attack: Bite +38 melee
Damage: Bite 4d8+27
Special Attacks/Actions: Frenzy, improved grab, swallow whole
Abilities: Str 46, Dex 10, Con 34, Int 2, Wis 16, Cha 13
Special Qualities: Hold breath
Feats: Awesome Blow; Improved Bull Rush; Improved Critical (bite); Improved Initiative; Improved Natural Attack (bite); Power Attack; Toughness (7)
Skills: Spot +44 and Swim +26
Advancement: 39-114 HD (Colossal)
Climate/Terrain: Any aquatic
Organization: Solitary or pair
Treasure/Possessions: None

Source: Dragon #318

Frenzy (Ex): If a liopleurodon is reduced to less than half its normal maximum hit points, It flies into a terrible rage of frenzied activity. During a frenzy, the liopleurodon gains a +4 bonus to its Armor Class and attack rolls. Its swim speed gains a +30 foot bonus, and if it makes a full attack action it gains an additional bite attack. The frenzy persists for minute, after which the liopleurodon becomes fatigued. A liopleurodon cannot enter a frenzy while it is fatigued.

Improved Grab (Ex): To use this ability, a liopleurodon must hit an opponent of up to one size smaller with its bite attack. It can then attempt to start a grapple as a free action without provoking an attack of opportunity. If it wins the grapple check, it establishes a hold and can try to swallow the foe the following round.

Swallow Whole (Ex): A liopleurodon can try to swallow a grabbed opponent of up to two sizes smaller by making a successful grapple check.

The swallowed creature takes 2d8+8 points of bludgeoning damage and 8 points of acid damage per round from the liopleurodon's gizzard. A swallowed creature can cut its way out by using a light slashing or piercing weapon to deal 45 points of damage to the gizzard (AC 20). Once the creature exits, muscular action closes the hole; another swallowed creature must cut its own way out.

A Colossal liopleurodon's gizzard can hold a Huge, 8 Large, 32 Medium, or 128 Small or smaller opponents.

Hold Breath (Ex): A liopleurodon can hold its breath for a number of rounds equal to 8 times its Constitution score before it risks drowning.

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

Skills: A liopleurodon has a +8 racial bonus on any Swim check to perform a special action or avoid a hazard. It can always choose to take to on a Swim check, even if distracted or endangered. It can use the run action while swimming, provided it swims in a straight line.

Liopleurodons often hunt near ocean shorelines and aren't afraid to surge out of the surf onto a beach to catch creatures that come too close to the edge of the sea. They attack with a powerful bite.