Monofin is a type of swimfin used in many water sports as a swimming aid. A single rigid flat surface is attached to swimmer’s feet to increase efficiency and speed. In mermaid world, we love monofins for their mermaid-like appearance. You can buy a monofin as a part of the mermaid tail set or separately. They come in three colours to choose from pink, blue or black. The only difference is colour, this is handy if your mermaid wants to match her outfit without her tail on that hides the Magic Fin Monofin.