Tail and Tutorial: Rogue Siren
Modeling the Tail: Lopti of Some Like it Blue
This is not an inexpensive project, and it is very time consuming. Custom silicone tails start at around $2000, after this tutorial, you will understand why. Materials alone can cost over $1000, they will be covered in the next step.
Expense alone is why I wouldn't recommend this as your first mermaid tail. Try a fabric or neoprene tutorial first. Swim in a monofin. Figure out if mermaiding is for you!
These tails are heavy! Depending on how thick you cast your scales and fins (more on this later), you could end up with a tail weighing 35lbs or more! Not only are they heavy, but they bind your legs and feet together. Be sure you are a confident swimmer, and have a buddy before attempting to swim in one.
They also take a lot of care! This will be covered at the end, but the overall effect is worth it! These are the most realistic and fully swimmable tails you see around! The final texture and feel is just like a fish.
WARNING: Tailmaking is addicting!
Looking for more info on mermaiding? Check out Mernetwork. It is an amazing resource.