Kystbåren
With the Havbåren being closest to humans, it is perhaps unsurprising that many of the Elven traits persist in the Kystbåren.
Ability Score: Strength +2 (Base ability scores cannot be added to Strength), Dexterity +1
Sea Legs: The innate sense of balance of the Havbåren is present in their offspring.
You suffer no penalty for terrain made difficult by warrant of its motion. You have advantage on rolls to avoid being knocked prone.
Aquatic Adaptations: While the lungs of Kystbåren are not as developed enough to warrant the benefits of Havbåren, they still retain other benefits.
You have a swimming speed equal to your speed.
Human Appearance: Provided your ears are hidden, you appear human to any onlooker.