Walrus (CR 2)

Large Animal
Alignment: Always neutral
Initiative: -1 (Dex); Senses: low-light vision, Listen +7, and Spot +7

AC: 12 (-1 size, -1 Dex, +4 natural), touch 8, flat-footed 12
Hit Dice: 5d8+5 (27 hp)
Fort +5, Ref +3, Will +2
Speed: 10 ft., swim 30 ft.
Space: 10 ft./5 ft.
Base Attack +2; Grapple +9
Attack: Bite +4 melee
Full Attack: Bite +4 melee
Damage: Bite 1d6+4
Special Attacks/Actions: -
Abilities: Str 17, Dex 9, Con 12, Int 2, Wis 13, Cha 6
Special Qualities: Hold breath
Feats: Alertness; Endurance
Skills: Listen +7, Spot +7, and Swim +11
Advancement: 6-9 HD (Large)
Climate/Terrain: Cold aquatic
Organization: Solitary, pair, or herd (3-8)
Treasure/Possessions: None

Source: Frostburn

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

Skills: A walrus 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.

Walruses are inclined to simply avoid strange or hostile creatures, but they can be territorial. Their large tusks can be dangerous weapons.