Ixitxachitl, Average (CR 1)

Small Aberration (Aquatic)
Alignment: Always chaotic evil
Initiative: +3 (Dex); Senses: darkvision 60 ft., Listen +3, and Spot +3

AC: 16 (+1 size, +3 Dex, +2 natural), touch 14, flat-footed 13
Hit Dice: 1d8+1 (8 hp)
Fort +1, Ref +3, Will +3
Speed: Swim 30 ft.
Space: 5 ft./5 ft.
Base Attack +0; Grapple -3
Attack: Bite +2 melee
Full Attack: Bite +2 melee
Damage: Bite 1d6+1
Special Attacks/Actions: -
Abilities: Str 12, Dex 16, Con 13, Int 12, Wis 13, Cha 7
Special Qualities: -
Feats: Dodge
Skills: Hide +11, Knowledge (nature) +3, Listen +3, Spot +3, Swim +9, and Tumble +6
Advancement: By character class
Climate/Terrain: Warm aquatic
Organization: Solitary, pair, pod (5-12 plus 1 2nd-level cleric), or shoal (10-100 plus 5 2nd-level clerics, 2 5th-level clerics, and 20-200 slaves)
Treasure/Possessions: No coins, no goods, double items (wearable items only)

Source: Monster Manual II

Individually, ixitxachitls are quite weak. They seldom attack unless they have overwhelming numbers or the opportunity to spring an ambush. They have been known to conceal themselves in the sand and muck of the sea bottom, waiting for enemies to pass by so they can rush in among them.

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.