The material below is Open Game Content from a 3PP Source

Gar, Giant

This fish is enormous—a sleek predator with bony scales and a long set of toothy jaws.

Giant Gar (CR 6; 2,400 XP)
N Huge animal (aquatic)
Init +4; Senses low-light vision; Perception +11
DEFENSE
AC 19, touch 8, flat-footed 19
(+11 natural, –2 size)
hp 73 (7d8+42)
Fort +11, Ref +7, Will +5
OFFENSE
Speed swim 60 ft.
Melee bite +14 (2d6+15 plus grab)
Space 15 ft.; Reach 15 ft.
Special Attacks swallow whole (2d6+10 bludgeoning damage, AC 15, hp 7)
STATISTICS
Str 30, Dex 10, Con 23, Int 1, Wis 13, Cha 2
Base Atk +5; CMB +17 (+21 grapple); CMD 27 (can't be tripped)
Feats Improved Initiative, Iron Will, Lightning Reflexes, Power Attack
Skills Perception +11, Swim +18
ECOLOGY
Environment temperate freshwater
Organization solitary, pair, or school (3–6)
Treasure none

Although typical gars are frightening enough, tales of enormous giant gars that lurk in the deepest rivers and lakes persist in many regions. These creatures are true monsters, often growing to lengths of 30 feet or more and capable of swallowing a horse and rider in a single gulp. Fortunately, giant gars are much rarer than their smaller kin.

Giant gars are often kept as pets and guard animals by aquatic creatures such as merrows, scrags (aquatic trolls), and the rare sea hags who dwell in freshwater dens.