Ahuizotl (CR 6)

Large Aberration (Aquatic)
Alignment: Usually chaotic evil
Initiative: +2 (Dex); Senses: darkvision 60 ft. and Spot +7
Languages: Common

AC: 17 (-1 size, +2 Dex, +6 natural), touch it, flat-footed 15
Hit Dice: 7d8+14 (45 hp)
Fort +4, Ref +4, Will +5
Speed: 20 ft., swim 40 ft.
Space: 10 ft./5 ft. (10 ft. with tail hand)
Base Attack +5; Grapple +14
Attack: Tail hand +10 melee
Full Attack: Tail hand +10 melee and bite +4 melee
Damage: Tail hand 1d6+5, bite 2d6+2
Special Attacks/Actions: Blinding strike, drowning, improved grab
Abilities: Str 21, Dex 14, Con 14, Int 12, Wis 11, Cha 15
Special Qualities: Voice mimicry
Feats: Combat Reflexes; Skill Focus (Bluff); Weapon Focus (tail, hand)
Skills: Bluff +13, Diplomacy +4, Disguise +2 (+4 acting), Hide +6, Intimidate +4, Spot +7, and Swim +20
Advancement: 8-14 HD (large); 15-21 HD (Huge)
Climate/Terrain: Any warm freshwater
Organization: Solitary
Treasure/Possessions: Standard

Source: Fiend Folio

Blinding Strike (Ex): If an ahuizotl scores a successful critical hit with its tail hand or its bite, the victim becomes blinded permanently

Drowning (Ex): If an ahuizotl pins a grappled victim while in water of any depth, the ahuizotl holds its victim underwater. The victim can hold its breath for a number of rounds equal to twice its Constitution score. When this time limit is reached, it must make a Constitution check (DC 10) each round to continue holding its breath; each round the DC increases by 1. When the victim fails one of these Constitution checks, it begins to drown. In the first round, it falls unconscious (0 hp). In the following round, it drops to -1 hit points and is dying. In the third round, it drowns.

Improved Grab (Ex): If an ahuizotl hits an opponent that is at least one size category smaller than itself with its tail hand attack, it deals normal damage and attempts to start a grapple as a free action without provoking an attack of opportunity (grapple bonus +14). It can immediately attempt to drown its victim if it is in water. Thereafter, the ahuizotl has the option to conduct the grapple normally, or it can simply use its tail hand to hold the opponent (-20 penalty on grapple check, but the ahuizotl is not considered grappled). In either case, each successful grapple check it makes during successive rounds automatically deals tail hand damage.

Voice Mimicry (Su): An ahuizotl can mimic spoken voices with unnatural ease. With a successful Bluff check, it can mimic a specific person's voice perfectly.

Skills: Ahuizotls have a +8 racial bonus on any Swim check to perform some special action or avoid a hazard and can always choose to take 10 on Swim checks, even if distracted or endangered.

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.