Mudmaw (CR 7)

Large Magical Beast
Alignment: Always neutral
Initiative: +5 (+1 dex, +4 Improved Initiative); Senses: darkvision 60 ft., low-light vision, and scent

AC: 17 (-1 size, +1 Dex, +7 natural), touch 10, flat-footed 16
Hit Dice: 8d10+24 (68 hp); DR: 10/magic
Fort +9, Ref +7, Will +5
Speed: 20 ft., swim 30 ft.
Space: 10 ft./10 ft.
Base Attack +8; Grapple +7
Attack: 2 tentacle rakes +11 melee and bite +6 melee
Full Attack: 2 tentacle rakes +11 melee and bite +6 melee
Damage: Tentacle rake 1d6+4, bite 1d8+2
Special Attacks/Actions: Constrict 2d8+6, Improved grab, spell-like abilities, trample 2d6+6
Abilities: Str 19, Dex 12, Con 17, Int 3, Wis 12, Cha 16
Special Qualities: SR 18
Feats: Improved Initiative; Iron Will; Track
Skills: Hide +6*, Survival +3, and Swim +12
Advancement: 9-16 HD (Large); 17-24 HD (Huge)
Climate/Terrain: Warm marsh
Organization: Solitary or pair
Treasure/Possessions: None

Source: Monster Manual II

Constrict (Ex): With a successful grapple check, a mudmaw can crush a grabbed opponent, dealing 2d8+6 points of bludgeoning damage.

Improved Grab (Ex): If a mudmaw hits an opponent that is at least one size category smaller than itself with a tentacle rake attack, it deals normal damage and attempts to start a grapple as a free action without provoking an attack of opportunity (grapple bonus +24, including +8 racial bonus on grapple checks). If it gets a hold, it also constricts in the same round. Thereafter, the mudmaw has the option to conduct the grapple normally, or simply use its tentacle to hold the opponent (-20 penalty on grapple check, but the mudmaw is not considered grappled). In either case, each successful grapple check it makes during successive rounds automatically deals tentacle rake damage.

Spell-Like Abilities: At will - slow, soften earth and stone, water walk. Caster level 5th; save DC 13 + spell level.

Trample (Ex): As a standard action during its turn each round, a mudmaw can trample opponents at least one size category smaller than itself. This attack deals 2d6+6 points of bludgeoning damage. A trampled opponent can attempt either an attack of opportunity at a -4 penalty or a Reflex save (DC 18) for half damage.

Scent (Ex): A mudmaw can detect approaching enemies, sniff out hidden foes, and track by sense of smell.

Skills: A mudmaw receives a +20 bonus on Hide checks when in water.

A mudmaw typically tries to grab creatures two or more size categories smaller than itself with its tentacles and drag them under the water to drown. Against larger creatures within 40 feet, it uses slow, then lunges from the water at a full charge, trampling its prey before grabbing it and returning to the water. A mudmaw doesn't attack if it can't reach its prey with its tentacles or with a single 40-foot charge. Larger creatures, or those that prove to be a threat, find pursuing the monster difficult because it uses soften earth and stone to turn the edge of the water into a quagmire, then swims away or uses water walk to cross it.