When determining your character’s ability scores, increase one score by 2 and increase a different score by 1, or increase three different scores by 1. Follow this rule regardless of the method you use to determine the scores, such as rolling or point buy. The “Quick Build” section for your character’s class offers suggestions on which scores to increase. You can follow those suggestions or ignore them, but you can’t raise any of your scores above 20.

You can speak, read, and write Common and Draconic. You also choose one other language you are proficient in based on your characters upbringing.

Axolotl Dragonborns are little, being 4 feet tall and weighing between 60 - 90 pounds. Your size is small.

You have a base walking speed of 25 feet and swimming speed of 30 feet.

You have both gills and lungs thus you're able to breathe on land and underwater.

You're survival instincts have adapted for any danger you might encounter in the depths below. While underwater you gain Tremorsense of 30 feet.

Given the right conditions, your body was built to withstand most poisons. You have advantage on saving throws against the poisoned condition and you have resistance to poison damage. 

Your system cannot stand high temperatures. Staying too long in extreme heat gives you 1 point of exhaustion and you lose your advantage on disease saving throws until you finish a long rest.  Trying to take a short or long rest while in extreme heat doesn't regain any hitpoints or spell slots.

You have advanced regenerative properties. If you lose any body part you roll a d20.  You take 30 and subtract it with your d20 result +your Constitution modifier, resulting on how many it will take for your limb to fully regrow back.