Crippling Impact. If the pirarucu moves at least 20 feet straight toward a creature and then hits it with a slam attack on the same turn, that target must succeed on a DC 12 Constitution saving throw or gain 1 level of exhaustion. Water Breathing. The pirarucu can breathe only underwater.
Slam. Melee Weapon Attack: +7 to hit, reach 5 ft., one target. Hit: 10 (2d4+ 5) bludgeoning damage. Tail. Melee Weapon Attack: +7 to hit, reach 10 ft., one target. Hit: 10 (1d10 + 5) bludgeoning damage. If the target is a medium or smaller creature, it must succeed on a DC 12 Strength saving throw or be knocked prone.