Clan Name: Ayame Clan
Appearance: Members of this clan possess two appears one called their human form and the other called their mer form often the only difference between the two is the presence of their mer features in the appropriately named form. Traits considered mer features are gills, webbing, tails, tentacles, and such which are adapts to live underwater. Otherwise, they mostly appear as normal humans.  
History: It's common sense that all life originated from the water at one point in it's past. Ayame have a very simple history of being a deviation of evolution. Sometime in the past a small number of humans gravitated back towards the water for numerous reasons and some of their offspring readapted to aquatic life through the evolution of new KKG, slowly giving rise to this clan.

Living mostly near water sources due to their ability to go back and forth it is not uncommon for Ayame to have one parent who is not adapted to aquatic life. Due to that fact many of the newest generations will occasionally find work as Ninja or other such land based jobs as they and their aquatic parent live with the non aquatic one.
Ability Names: Aquatic Adaptation
Ability Descriptions:
Different World
Being adapted to be capable of living underwater has possessed a long term unforeseen effect on Ayame members. No longer able to learn Fire Release they can learn Sound Release as a basic element in it's place. Sound Release is not exclusive to the clan, just one they have a natural affinity towards the way land ninja have towards fire.

Advanced Release
Those within this clan are able to sense weather hours before it actually happens and disaster weather days prior. Possessing some degree of weather control they can change the weather in topics though not induce things like tsunamis or other disaster level weather events. Sometimes when they're using Water, Sound, Wind, or Lightning Releases things like dark clouds or the like will form giving the illusion of weather manipulation. Also able to have their water or sound release spawn out of the water jutsu of other's although they can not destroy or manipulate the jutsu of other's directly.

Aquatic Senses
Able to see clearly underwater, breathe underwater, hear clearly under water, etc like any other aquatic creature. Able to detect vibrations/electrical fields in the water up to 60 meters and within 12 feet of it so long as they're touching water. While most Ayame retain a sensory distance of 12 feet from the waters edge their whole life if they've taken one of the following specialties they unlock the ability to train it up 1,000 words per 3 meter's until they reach the same distance they can sense in the water. Sensory.They must always have some part of them touching water to do this even after training.  

Mythical Physique
While possessing the same lifespan as humans, those with an active KKG can sometimes remain young in appearance for their whole life.

Two Forms
They can shift between an aquatic adapted form which is as good underwater as any other aquatic creature and far better than humans within it. However, it should be noted some of their human form limbs become replaced by their aquatic ones, if something even mere fabric is separating the limbs that should normally transform, they can not shift that part of them. If they attempt shift it results in an incomplete one which can only maneuver the water as any human could.  

Fishy Friends
An Ayames 'tail' will be covered in scales or skin which it's covered in determines their ability to speak to aquatic/semi aquatic creatures as they can only speak to creatures whose bodies are covered in the one which matches them. Those with tentacles may only speak to octopi and other tentacled creatures, while those with shark features may only speak to sharks.

Chakra Costs: N/A Outside of normal costs
Requirements:
Can't learn Fire Release in any way including if they got a limited that would normally provide such.
Must have Water Release as an element.
Can't transform if limbs that transform are obstructed.
Jutsu: To Be Made.

The advantages I'd allow is that you can set the normal weather in a topic as you see fit, be immune to some of THAT weather, and sense weather. Can't manipulate elements outside of what nature does naturally, and if you chose a thunderstorm it wouldn't just attack your enemies only conveniently for example.

Weather Release isn't really an advanced elemental nature along with Sound Release.

As I'd noted Sound Release is available in canon as sound jutsu so it'd be non-elemental and not limited to this clan.~

https://naruto.fandom.com/wiki/Weather_Manipulation This isn't allowed at "full power" on site as one of those OP filler things that are the main examples of what I'd say no to in unranked jutsu.

If you'd want weather control it wouldn't give access to all elements or manifestation of them. You'd need to balance it along the line of my suggestions.

Storm's an Omega-level mutant in DC Comics for a reason lol. It's an omni-conceptual power that's too vague with multiple fields and elements.

Vibration sensing in water needs specific ranges that you can decide. "Of the end of it" should be removed as it sounds like if you're in the ocean at each beach you can sense things lol idk.

that should do the trick for most of it I think.

Approved~