You can breathe air and water. You have a swim speed of 25ft.

You can cast the Alter Self spell, however you can only use the Aquatic form listed in the spell's description, you can use this feature once in a Long rest.

You can read the thoughts and speak to the minds around you, as 1st Level you gain Telepathy with a 30ft range, however your thoughts are broadcast to everyone in range. At 5th level, you develop the ability to focus your thoughts, you may communicate with one or two people privately at once, otherwise you broadcast to all creatures in range. At 8th level, your range increases to 60ft and you can control whether your thoughts are broadcast within range or not.

Adapted to even the most extreme ocean depths, you have resistance to cold damage, and you ignore any of the drawbacks caused by a deep, underwater environment.