Full Moon Mermaid Spell

To start this spell you will need these ingredients...
Sea Salt
Blank Page in a Spell Book (Any spell Book works)
Water
Full Moon
Magic!

Pour the water in a circle around you. Then open your spell book, and place your sea salt in the shape of a fin, like this: . Next place the spell book in the center of the circle and connect yourself with the full moon. In your head ask the moon for it's power, (You can meditate if you want ) then transmit that power to your book. Now add 3 drops of water to the fin. One on the left tip, on the right tip, and in the middle. Make sure the water touches the page. (You can put a paper towel, napkin, regular towel etc. under the page beforehand to protect the page underneath it.) Now for around 3-5 weeks you will act like a mermaid! This spell can help improve your diet as well because seafood is low in fat and has many minerals. You'll want to swim, shower, and take baths more often. And you can make siren calls! (a high pitch shriek.) Your singing voice can also improve as well as your swimming skill. Your hair might also grow faster. Side effects: Any other full moons could put you in a trance, making you seemingly sleep walk to the nearest available water, You may sweat more, Full moons affect you more. If the spell fails you MUST wait until the next full moon or your magical abilities and connections could become weak or dormant for as long as three full moons. Have fun!

I am sorry, but this spell and all spells that claim to magically change you into something other than the human you already are are completely fake. They will not work no matter how much you believe or how often you try. You simply will never, ever become a mermaid.

As above stated, you cannot physically transform into a mermaid. It's not possible. Spells work only with realistic expectations.
As for the effects that you stated, some of them are possible and there are spells on this site about achieving those goals.
To improve your diet, there are spells on this site to increase your motivation to stick to such a diet, but it still takes effort on your part to choose to eat healthy.
Increased hair growth might be possible in a glamour spell(realistically speaking; you won't wake up with four more inches of hair overnight), but there are also beauty products and rituals that can help stimulate your hair follicles.
To improve a singing voice, that would probably just take a lot of practice. I would recommend getting a teacher to help you out with tone and projection, but you can also cast a spell to increase your motivation and focus on the subject.
You can draw energy from full moons for certain spells on this site just as you can draw energy from new moons and other astrological occasions (meteor showers, eclipses, etc.) It really depends on the nature of the spell you're casting whether each makes the effects weaker or stronger.
If you get the chance to look around this site, I hope you find realistic spells that work for you. Best of luck

Sorry to burst youe bubble but your claims on mermaid are false as they do Not exist sorry to but the truth is the best information to help