There are various magical spells and potions that can accomplish the titanic task of transforming a human into a Mermaid. You would need to contact a professional witch, warlock, wizard, or sorcerer to look into your options. Otherwise, there are two easier methods of becoming a Mermaid. Firstly, those who fall in love with a mermaid or merman can temporarily transform into one. This only occurs when entering the sea above the mystical confines of an undersea Mermaid community such as Atlantis.
Secondly, there is a method some can do on their own. However, you must be a descendant of the lost continent of Atlantis as this is where all Mermaid’s originated. Even if it is an extremely distant relation the magic will work. You can determine this with a supernatural status spell. You can activate your latent mermaid genes by drinking a potion made of Atlantic seawater, Atlantic Dolphin milk, Atlantic Seahorse oil, Sea Grape Juice ( Caulerpa lentillifera ), Irish Moss ( Chondrus crispus ), Red Seaweed (Palmaria palmata), and, marine eelgrass (Zostera). The potion must fill a large conch shell, be mixed completely, and be drunk directly from said shell. The shell must be from the Atlantic ocean or an Atlantic seaside beach. In addition, the mermaid potion must be drunk while immersed in the ocean at least up to your neck under the light of a 100% full moon. The Atlantic Ocean seems to bear better results. Within an hour you should transform into a mermaid or merman. If nothing happens within two hours then you have no Atlantean heritage in your genetics or some unknown factor is blocking the magic. Most likely the ingredients weren’t exact. Substitutions will not work!