If it needs to be swimmable, then you probably want to use neoprene, the material used in wetsuits. A couple of scuba fins trimmed and fastened together would work well for the end of the tail, and provide a comfortable place for the feet.If you re on a budget, you can find used wetsuits and fins very cheaply on eBay. You could cut the inside seam on the two wetsuit legs and sew them together. The seam will need to be very strong, though, getting into a wetsuit is not easy, even one leg at a time. Better get the biggest wetsuit you can.
That would be a major project and you probably don t want to deal with the safety issues here either.Imagine someone swimming with both their legs bound up in a cloth mermaid tail and they drown because they can t keep afloat. You would be sued for sure.
hi, i am more into visual effects. however a friend of mine is into you kind of animation, and perhaps if you mail her she might be able to help you... her mail id is colouredge@gmail.com her name is sapna.