Octopi have the following traits:
Aquatic: Octopi can move in water without making Swim checks and cannot drown in water.
Improved Grab (Ex): To use this ability, a normal octopus must hit with its tentacle attack (which itself deals no damage). If it gets a hold, it automatically deals bite damage each round the hold is maintained. If a giant octopus successfully hits with a tentacle slam against a target smaller than itself, it can deal automatic bite damage each round or it can constrict (see below).
Constrict (Ex): A giant octopus that succeeds in grappling an opponent smaller than itself deals 1d4+5 points of damage per round as it constricts. Poison (Ex): Some small octopi have venomous bites. Bite: Fortitude save (DC 10 + 1/2 octopus’s Hit Dice + octopus’s Constitution modifier); initial and secondary 1d2 Strength damage.
Ink Cloud (Ex): Both the octopus and giant octopus can emit a cloud of jet-black ink as a free action. The normal octopus’s ink cloud is a 10-foot cube, while the giant octopus’s ink cloud fills a 20-foot cube. The cloud provides total concealment, which the octopus normally uses to escape a losing fight. All vision within the cloud is obscured.
Jet (Ex): An octopus or giant octopus can jet backward once a round as a full-round action, at a speed of 200 feet.
Low-Light Vision (Ex): Lizards can see twice as far as a human in starlight, moonlight, torchlight, and similar conditions of poor illumination. They retain the ability to distinguish color and detail under these conditions.
Skill Bonuses: Both octopi and giant octopi can change colors and squeeze into small spaces. They gain a +4 species bonus on Hide checks and a +10 species bonus on Escape Artist checks.
Bonus Feats: Normal octopi gain the bonus feats Weapon Finesse (bite) and Weapon Finesse (tentacles).
Octopus: CR 1/6 (1/2 if venomous); Small animal; HD 1/2 d8; hp 2; Mas 11; Init +3; Spd 5 ft., swim 30 ft.; Defense 15, touch 14, flat-footed 12 (+1 size, +3 Dex, +1 natural); BAB +0; Grap –3; Atk +4 melee (special, tentacles); Full Atk +4 melee (special, tentacles), –1 melee (1d4, bite); FS 5 ft. by 5 ft.; Reach 5 ft.; SQ Aquatic, improved grab, poison (DC 10), ink cloud, jet, low-light vision; AL none; SV Fort +2, Ref +5, Will +1; AP 0; Rep +0; Str 10, Dex 17, Con 11, Int 3, Wis 12, Cha 3.
Skills: Escape Artist +13, Hide +7, Listen +5, Move Silently +5, Spot +5.
Feats: Weapon Finesse (bite, tentacles).
Advancement: 1–2 HD (Small); 3–7 HD (Medium).
Giant Octopus: CR 8; Large animal; HD 8d8+8; hp 44; Mas 13; Init +2; Spd 10 ft., swim 30 ft.; Defense 18, touch 11, flatfooted 16 (–1 size, +2 Dex, +7 natural); BAB +6; Grap +15; Atk +10 melee (1d4+7, tentacle slam); Full Atk +10 melee (1d4+5, 8 tentacle slams), +5 melee (1d8+2, bite); FS 10 ft. by 10 ft.; Reach 10 ft.; SQ Aquatic subtype, improved grab, constrict, ink cloud, jet, low-light vision; AL none; SV Fort +7, Ref +8, Will +3; AP 0; Rep +0; Str 20, Dex 15, Con 13, Int 2, Wis 12, Cha 3.
Skills: Escape Artist +12, Hide +2, Listen +5, Move Silently +4, Spot +5.
Advancement: 9–12 HD (Large); 13–24 HD (Huge); 25–42 (Gargantuan).