Hold Breath. A bunyip can hold its breath for an hour.
Blood Rage. If a creature enters the same body of water as the bunyip and is missing more than half of its hit points, the bunyip has advantage on attack rolls made against that creature, and critical hits on a 19 or 20 on the attack rolls made against that creature.
Roar. The bunyip lets out a terrifying roar. All creatures in a 100-foot radius must succeed on a DC 13 Wisdom saving throw or become frightened. Whether or not the save is successful, creatures in the area are immune to the roar of that bunyip for 24 hours.
Bite. Melee Weapon Attack: +5 to hit, reach 5 ft., one target. Hit: 5 (2d4 + 3) piercing damage.
Slam. Melee Weapon Attack: +5 to hit, range 5 ft., one target. Hit: 7 (1d6 + 3) bludgeoning damage. On a hit, the target must succeed on a DC 13 Strength saving throw or be knocked prone.