This post was inspired by the awesome artwork of Drachenmagier seen here and here. I started with the stats for a Grizzly Bear from the SRD, Then for the Dire Trout (inspired by Ray Trolls amazing art) I started with the stats for a Shark from the SRD.
AC 6 
Atk 2 claws (1d6), 1 bite (1d10) or 1 Tail Thrash (1d6)
Special: Hug (2d6).
It is said that a sorcerer of the north, who had a great fondness for hunting, would rework his beasts to include just enough of the prey animals to speed their assault. He crossed hound to fox, beagle to rabbit, bulldog to boar, and his prized trained hunting bears with the great dire trout of the north. In his madness he summoned what he thought the ultimate prey, an infernal prince from the bowels of the underworld. The Devil took him and many of his creations to places of pain living men cannot even comprehend, and only a few of the chimeric beasts disappeared into the night safely. The aquatic bear is a great hulking beast, big as its grizzly fore bearers, with the wicked tusks of the Dire Trout (Oncorhynchus rastrosus) and a massive salmonoid tail. The bear can make a thrashing and clawing attack utilizing its rear claws and tail, or a bitting and clawing attack, but not both in the same round, A successful tail thrash leaves the PC prone for one turn. The Aquatic bear is elegant in water, and only slightly clumsy on land owing to stubby muscular hind legs and a thick muscular tail. Aquatic Bears can breath salt water and air freely prior to spawning, but during the mating season, or when quite young, they can only breath freshwater (and air) and will seek out inland ponds and pools to raise their young. Aquatic Bear males only mate once, growing much larger than before and using the stats below, they die after the breeding season leaving the females to rear the young. A female Aquatic Bear protecting her young will get a +1 to hit and fight to -2 HP, below 0 HP she will die after the combat even if victorious.
- Bear, Aquatic Male (during mating season): HD 7; AC 6 ; Atk 2 claws (1d6+1), 1 bite (1d10+1) or 1 tail thrash (1d6+1); Move 12; Save 9; AL N; CL/XP 7/600; Special: Hug (3d6).
Cloak of the Bearmaiden⌗
There exists an elder order of north-women who use witchcraft to enchant the skins of slain female Aquatic Bears to allow for transformation when donned as a cloak. The cloak is capable of turning anyone into a Female Aquatic Bear when donned after performing the appropriate rituals, and to return them to their own form at will. For each day spent in the form of the Aquatic Bear the wearer becomes more like the beast and less likely to take off the cloak (savings throw with a -1 for each full day after the first), which is why the bearmaidens only wear them a short while. If slain the wearer remains an Aquatic Bear, and if skinned and the skin is fashioned into garments it will function exactly as the original cloak.
Atk 1 bite (1d6+2)
Move 0 (Swim 24)
Special: Fang Hook.
Dire Trout are salmonoid horrors to the north, worshipped and feared by the painted savages of old for their cyclic lives, great size, and prized scintillating skins, the Dire Trout was both food and totem to those brave enough to face them. 6-8 ft long, steel grey or silver when at sea, brightly colored when returning to freshwater to spawn, the Dire trout is a hulking monstrous fish with massive saber teeth that appear during spawning season on the male of the species. On a successful bite attack the Dire trout has a 1 in 6 chance of grasping the victim in its maw and pulling it under to drown (2 in 6 when fanged), the victim can attempt to fight its way free with a -2 penalty to-hit. When slain their flesh can be smoked to provide rations enough for a 1d6 weeks, and the skin can be fashioned into armor with AC 6.