you gain proficiency in perception checks

You can breathe air and water

 You’re immune to poison damage and the poisoned condition.

Any creature that grapples you or otherwise comes into direct contact with your 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 you can repeat the saving throw at the end of each of its turns, ending the effect on itself on a success.

You can also apply this poison to any piercing weapon as part of an attack with that weapon, though when you hit the poison reacts differently. The target must succeed on a DC 12 Constitution saving throw or take 2d4 poison damage.

Your long jump is up to 25 feet and your high jump is up to 15 feet, with or without a running start.

 If you fail to immerse yourself in water for at least 1 hour during a day, you suffer one level of exhaustion at the end of that day. You can only recover from this exhaustion through magic or by immersing yourself in water for at least 1 hour. Languages. You can speak, read, and write Grung

Your dexterity increases by 2 and your constitution increases by 1

A halfling reaches adulthood at the age of 20 and generally lives into the middle of his or her second century.

Grungs are mostly lawful, being raised on a strict caste system. 

Grungs average about 2 1/2 and 3 1/2 feet tall. Your size is Small.

Your base walking speed is 25 feet and a climbing speed of 25

You can speak, read, and write Common and Halfling. The Halfling language isn’t secret, but halflings are loath to share it with others. They write very little, so they don’t have a rich body of literature. Their oral tradition, however, is very strong. Almost all halflings speak Common to converse with the people in whose lands they dwell or through which they are traveling.