I was looking though my Bestiary and I didn't see a feral/dire template. Does it exist in any published material yet?
Feral template was in Savage Species. That was 3.0 tho, and horribly broken. You'll probably want to tinker with it before you unleash it.
Fast Healing, Imp. Grab, Pounce, Rend, Rake, DR, Claws, d10 HD, +6 Natural Armour, Spd +10ft., Darkvision, whew!
All for a +1 lvl adjustment. Yep, preeety broken.
You probably don't really need a dire template. You can just give it some more hit dice and possibly make it a giant creature.
Here is an advanced crocodile with a size increase and the giant template:
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CROCODILE CR 12
Male Crocodile
Gargantuan Animal
Init +4; Senses Low-Light Vision; Perception +11
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DEFENSE
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AC 17, touch 6, flat-footed 17. . (-4 size, +11 natural)
hp 142 (3d8+84)
Fort +15, Ref +8, Will +7
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OFFENSE
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Spd 20 ft., Sprint x2 (1/minute), Swimming (30 feet)
Melee Bite (Crocodile) +16 (3d6+11) and
. . Tail Slap (Crocodile) +11 (4d6+5) and
. . Unarmed Strike +16/+11 (1d8+11)
Space 20 ft.; Reach 15 ft.
Special Attacks Death Roll, Grab
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STATISTICS
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Str 33, Dex 10, Con 25, Int 1, Wis 12, Cha 2
Base Atk +5/+0; CMB +24 (+28 Grappling); CMD 34 (38 vs. Trip)
Feats Improved Critical: Bite, Improved Initiative, Iron Will, Run, Skill Focus: Perception, Skill Focus: Stealth
Skills Fly -6, Perception +11, Stealth +2, Swim +19Modifiers +8 Stealth in water
Languages
SQ Hold Breath (x4) (Ex)
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SPECIAL ABILITIES
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+8 Stealth in water (Ex) You gain a bonus to Stealth Checks under the listed conditions.
Death Roll (Ex) If you grapple a target, you can roll to inflict bite damage and knock the creature prone.
Grab (Huge) (Ex) You can start a grapple as a free action if you hit with the designated weapon.
Hold Breath (x4) (Ex) You can stay under water longer than normal.
Low-Light Vision See twice as far as a human in low light, distinguishing color and detail.
Run You run faster than normal.
Sprint x2 (1/minute) (Ex) 1/minute, increase your land speed by a factor of 2
Swimming (30 feet) You have a Swim speed.
Here is the dire crocodile:
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CROCODILE, DIRE CR 9
Male Crocodile, Dire
Gargantuan Animal
Init +4; Senses Low-Light Vision; Perception +14
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DEFENSE
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AC 21, touch 6, flat-footed 21. . (-4 size, +15 natural)
hp 138 (12d8+84)
Fort +15, Ref +8, Will +8
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OFFENSE
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Spd 20 ft., Sprint x2 (1/minute), Swimming (30 feet)
Melee Bite (Crocodile, Dire) +18 (3d6+13) and
. . Tail Slap (Crocodile, Dire) +13 (4d8+6) and
. . Unarmed Strike +18/+13 (1d8+13)
Space 20 ft.; Reach 15 ft.
Special Attacks Death Roll, Grab, Swallow Whole (3d6+13, AC 17, 13 HP)
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STATISTICS
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Str 37, Dex 10, Con 25, Int 1, Wis 14, Cha 2
Base Atk +5/+0; CMB +26 (+30 Grappling); CMD 36 (40 vs. Trip)
Feats Improved Critical: Bite, Improved Initiative, Iron Will, Run, Skill Focus: Perception, Skill Focus: Stealth
Skills Fly -6, Perception +14, Swim +21Modifiers +8 Stealth in water
Languages
SQ Hold Breath (x4) (Ex)
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SPECIAL ABILITIES
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+8 Stealth in water (Ex) You gain a bonus to Stealth Checks under the listed conditions.
Death Roll (Ex) If you grapple a target, you can roll to inflict bite damage and knock the creature prone.
Grab (Huge) (Ex) You can start a grapple as a free action if you hit with the designated weapon.
Hold Breath (x4) (Ex) You can stay under water longer than normal.
Low-Light Vision See twice as far as a human in low light, distinguishing color and detail.
Run You run faster than normal.
Sprint x2 (1/minute) (Ex) 1/minute, increase your land speed by a factor of 2
Swallow Whole (3d6+13, AC 17, 13 HP) (Ex) You can swallow smaller targets whole.
Swimming (30 feet) You have a Swim speed.
If you look, they are pretty close to each other. The CR is different and the stats don't line up perfectly but it works in a pinch.