Selkie

Selkie reside within the icy waters of the Moonshae Isles, referring to the mysterious lands above the ocean, where humans had settled, as the overworld. Believed to have once been seals gifted with the magic to obtain mortal forms, they are capable of shedding their water dwelling forms so that they may mingle with the species of the overworld.

Strangers Ashore

In their human form, selkies would visit the overworld and purchase supplies, or even information/ They generally, however, had very limited knowledge regarding the surface world.
They are known to fall in love easily and quickly, and even to be loyal for many years, but they will abandon their families sooner or later, and, if kept against their will, can turn dangerously violent. As you create your selkie character it can be helpful to decide on a couple of behavioral quirks that reflectyour fey nature.

Amorous Encounters

The selkie are renowned for their many amorous encounters with human settlers along the coasts--married or unmarried. A selkie in human form is said to be a beautiful creature, almost magical seductive powers over humans. Half-blooded humans born from such encounters often develop selkie like traits later in life; Webbed feet and fingers, an unnatural affinitry for the sea, or sorcerous abilities of unknwon origin. Should a human wish to make contact with a selkie, there was once an ancient rite to follow. it was believed that shedding seven tears into the sea at high tide would summon forth a selkie.
If someone went missing while out on the ebb, or at sea, it was inevitably said that their selkie lover had taken them to their watery domain -- assuming, of course, they had not attracted the eye of a lothsome merfolk instead.

HOMEBREW

Selkie

ability score increase: Choose one of: (a) Choose any +2; choose any other +1 (b) choose three different +1

age: Selkie mature quickly, reaching adulthood in their early teens. They show no signs of aging beyond that point and rarely live longer than 75 years.

alignment: As gentle beings who deem violence inessential to their whimsical lifestyle, selkie are typically neutral good. If confined against their will, selkies can turn dangerously violent.

Size: Medium

speed: Your base walking speed is 30 feet.

Languages: You can speak, read, and write Common and one other language that you and your DM agree is appropriate for your character.

race features:
Fey. Your creature type is fey, rather than humanoid.
Shaman.You have proficiency in one of the wollowing skills of your choice:Medicine, Nature, Stealth, or Survival.
Child of the High Sea. You have resistance to cold damage. You're also naturally adapted to cold climates, even in the most extreme ocean depths.
Selkie Magic. You can cast charm person and fog cloud with this trait, using either Whisdom or Charisma as your spellcasting ability (you choose at the time of character creation). Once you cast either spell, you can't cast it again with this trait until you finish a short or long rest.
Legacy of Surminare.As an action, you can transform into a human or revert to your natural form, which is a seal. Your game statistics, other than your speed, are the same in both forms. When you transform into a human, you magically shed the furskin of your seal form. To return to this form you must have your furskin in hand, if you lose the furskin, you can perform a 1-hour ceremoney to fashion a replacement. This ceremony can be performed during a short or long rest, and it destroys the previous furskin.