Do I need a monofin to swim in a mermaid tail?

[sea_echols]

Hello, I am thinking of getting a merman tail with the design of an orca. I have a question though; do I need a monofin to swim in a merman tail? I see everyone that swims with a mer-tail have a monofin inside, but I hardly see anyone without one and just using the tail only. Does anybody else only swim with just the tail? Would the tail by itself still keep the legs together like a monofin would?

[Merman Storm]

The monofin does 2 things:
It gives you a tail. Otherwise you would just have some fabric streaming behind you.
It provides propulsion. A monofin is better than normal swim fins for propulsion. That's why free divers use them.

[sea_echols]

Ok good to know then, well if that is the case then may I have your opinion on something? I am now looking for a monofin that looks close to an orca tail on the market. I came across this and I would like to know if you think in your opinion that this monofin looks somewhat like an orca tail? Sorry to bug you on this I would just like another person's opinion on it. I have the fin and an actual orca tail
from google images for comparisons. If you dont think so, do you have any recommendations?
https://www.bing.com/images/search?view=detailV2&ccid=rAPQxFp4&id=7AE364F73FAED604DFC8DA83FA650DF4FC643DA1&thid=OIP.rAPQxFp4qv95-XEs-7IrJgHaHa&mediaurl=https%3a%2f%2ftauchbar.ch%2fwp-content%2fuploads%2f2021%2f02%2fsweam-monofins-minos-600x600.jpg&cdnurl=https%3a%2f%2fth.bing.com%2fth%2fid%2fR.ac0 3d0c45a78aaff79f9712cfbb22b26%3frik%3doT1k%252fPQN ZfqD2g%26pid%3dImgRaw%26r%3d0&exph=600&expw=600&q=sweam+minos+monofin&simid=608007197414397449&FORM=IRPRST&ck=3A35696BA1E148EBADD5262662D05739&selectedIndex=5&ajaxhist=0&ajaxserp=0https://www.spearfishingworld.com/product_images/o/696/minos_noir_ok_zoom__91376_zoom.pnghttps://th.bing.com/th/id/OIP.d_heiLkX7yXlKDZZlFFFVAHaE7?pid=ImgDet&rs=1