SRD:Dire Shark

Dire Shark
Dire sharks attack anything they perceive to be edible, even larger creatures.

This monstrous fish can grow to a length of 25 feet and weigh more than 20,000 pounds.

Combat
Dire sharks bite with their powerful jaws, swallowing smaller creatures in one gulp.

Improved Grab (Ex): To use this ability, a dire shark must hit 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 in the following round.

Swallow Whole (Ex): A dire shark can try to swallow a grabbed opponent of up to one size smaller by making a successful grapple check. Once inside, the opponent takes 2d6+6 points of bludgeoning 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 a light slashing or piercing weapon by dealing 25 points of damage to the shark’s digestive tract (AC 13). Once the creature exits, muscular action closes the hole; another swallowed opponent must cut its own way out.

A Huge dire shark’s gullet can hold 2 Large, 8 Medium or Small, 32 Tiny, 128 Diminutive, or 512 Fine or smaller opponents.

Keen Scent (Ex): A dire shark can notice creatures by scent in a 180-foot radius and can detect blood in the water at a range of up to 1 mile.

Skills: A dire shark has a +8 racial bonus on any Swim check to perform some special action or avoid a hazard. It can always choose to take 10 on a Swim check, even if distracted or endangered.

It can use the run action while swimming, provided it swims in a straight line.

See Wikipedia Entry: Shark