Sea Tiger (CR 6)

Huge Animal
Alignment: Always neutral
Initiative: +1 (Dex); Senses: blindsight 100 ft. and low-light vision

AC: 19 (-2 size, +1 Dex, +10 natural), touch 9, flat-footed 18
Hit Dice: 10d8+30 (75 hp)
Fort +10, Ref +8, Will +5
Speed: 20 ft., swim 50 ft.
Space: 15 ft./10 ft.
Base Attack +7; Grapple +19
Attack: Bite +9 melee or claw +9 melee
Full Attack: Bite +9 melee and 2 claws +4 melee
Damage: Bite 2d8+4, Claw 1d6+2
Special Attacks/Actions: -
Abilities: Str 19, Dex 13, Con 17, Int 2, Wis 14, Cha 8
Special Qualities: hold breath
Feats: Endurance; Improved Bull Rush; Power Attack; Run
Skills: Hide +6 and Swim +12
Advancement: 11-20 HD (Huge)
Climate/Terrain: Any aquatic
Organization: Solitary, pair, or pod (5-20 plus 20% noncombatants)
Treasure/Possessions: None

Source: Monster Manual III

Blindsight (Ex): A sea tiger emits high-frequency sounds inaudible to other creatures that allow it to locate objects and creatures within 120 feet. A silence spell negates this and forces the sea tiger to rely on its vision, which is approximately good as a human's.

Hold Breath (Ex): A sea tiger can hold its breath for a number of rounds equal to 6 x its Constitution score before it risks drowning.

Skills: A sea tiger 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.

Carrying Capacity: A light load for a sea tiger is up to 700 pounds; a medium load, 701-1,400 pounds; and a heavy load, 1,401-2,100 pounds.

Sea tigers circle their opponents and rush in individually until an opponent either flees or dies.