race features:
Child of the Sea. You can breathe air and water. In addition, as an action you can transform your lower half into a tail with fins like a fish, whale, or another aquatic creature. While transformed your walking speed becomes 5 feet and you gain a swimming speed of 40 feet. You can end this transformation as a bonus action.
Friend of the Sea. Using gestures and sounds, you can communicate simple ideas with any beast that has an innate swimming speed.
Mastery of Air and Water. A child of the sea, you can call on the magic of elemental air and water. You can cast the cantrip fog cloud with this trait. Starting at 3rd level, you can cast gust of wind with it, and starting at 5th level, you can also cast wall of water with it. Once you cast a spell with this trait, you can't do so again until you finish a long rest. Charisma is your spellcasting ability for these spells.