Opabinia (CR 2)

Medium Aberration (Aquatic)
Alignment: Always neutral
Initiative: +2 (Dex); Senses: darkvision 60 ft., low-light vision, and Spot +7

AC: 14 (+2 Dex, +2 natural), touch 12, flat-footed 12
Hit Dice: 3d8 (19 hp)
Fort +3, Ref +3, Will +4
Speed: 30 ft., swim 30 ft.
Space: 5 ft./5 ft. (bite 10 ft.)
Base Attack +2; Grapple +5
Attack: bite +5 melee
Damage: Melee bite 1d6+4
Special Attacks/Actions: Improved grab, worry 1d6+4, extended reach, jagged bite
Abilities: Str 16, Dex 15, Con 14, Int 1, Wis 12, Cha 5
Special Qualities: -
Feats: Dodge, Stealthy
Skills: Hide +6, Move Silently +6, Spot +7, and Swim +11
Advancement: 5-8 HD (Medium), 9-12 HD (Large)
Climate/Terrain: Any land and underground (Eberron)
Organization: Solitary
Treasure/Possessions: None

Source: Dragon #348

Improved Grab (Ex) In order to use this attack, an opabinia must hit a Small or smaller creature with its bite attack. It can then make a grapple check as a free action without provoking an attack of opportunity. If it gets a hold, it can make worry attacks.

Worry (Ex) An opabinia shakes opponents grabbed in its jaws, dealing 1d6+4 damage every round it maintains the grapple.

Extended Reach (Ex) The mouth of an opabinia sits on a long trunk, granting its bite attack 10-foot reach.

Jagged Bite (Ex) An opabinia's bite leaves terrible tears in the flesh. Damage taken from an opabinia's bite does not heal naturally. Magical healing (such as with cure spells), fast healing, and regeneration work normally.

Skills An opabinia 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. An opabinias five eyes grant it a +4 racial bonus on Spot checks.

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.