Amphibious.

The grung can breathe air and water.

Poisonous Skin.

Any creature that grapples the grung or otherwise comes into direct contact with the grung's skin must succeed on a DC 12 Constitution saving throw or become poisoned for 1 minute. A poisoned creature no longer in direct contact with the grung can repeat the saving throw at the end of each of its turns, ending the effect on itself on a success.

Standing Leap.

The grung's long jump is up to 25 feet and its high jump is up to 15 feet, with or without a running start.

Water Dependency.

If the grung isn't immersed in water for at least 1 hour during a day, it suffers 1 level of exhaustion at the end of that day. The grung can recover from this exhaustion only through magic or by immersing itself in water for at least 1 hour.

Actions

Dagger.

Melee or Ranged Weapon Attack: +5 to hit, reach 5 ft. or range 20/60 ft., one target. Hit: 5 (1d4 + 3) piercing damage plus 5 (2d4) poison damage.

Shortbow.

Ranged Weapon Attack: +5 to hit, range 80/320 ft., one target. Hit: 6 (1d6 + 3) piercing damage plus 5 (2d4) poison damage.

Mesmerizing Chirr (Recharge 6).

The grung makes a chirring noise to which grungs are immune. Each Humanoid or Beast that is within 15 feet of the grung and able to hear it must succeed on a DC 12 Wisdom saving throw or be stunned until the end of the grung's next turn.

Grung Elite Warrior