You can breathe both in air and water.

The following traits only apply if you've been in water for at least 30 minutes within the last 2 days:

Once per short rest, as an action on your turn, you can regain, 1d4 + your constitution modifier, health.

Once per long rest, roll 1d6. If you roll a 6, you can regrow a severed limb.

Once per long rest, during a short rest, if you have no more hit dice left, then you may use one more free hit die.

You have disadvantage on ranged attack rolls and Wisdom (Perception) checks that rely on sight when you, the target of your attack, or whatever you are trying to perceive is in direct sunlight. This can be countered by wearing eye protection such as sunglasses or dimmed goggles.

Your Dexterity score increases by 2, and your Wisdom score increases by 2.

You reach adulthood at around 15, and live up to 100 years old. Your physical appearance remains similar to a child's for the remainder of your life.

Axolotl are most often good. Axolotl are good-hearted, and even the worst among them are more prank-prone than mean.

Axolotl are between 4 and 5 and a half feet tall and average about 50 pounds. Your size is Medium.

Your base walking and swimming speed are both 30 feet.

Accustomed to life underground, you have superior vision in dark and dim conditions. You can see in dim light within 120 feet of you as if it were bright light, and in darkness as if it were dim light. You can’t discern color in darkness, only shades of gray.

You can speak, read, and write Common, Undercommon, and Aquan.