I'm an adult size 11 wide and I was hesitant to try an adult large/large as this seller had listed. But thank goodness I went with large, it fits pretty snug which is what I was looking for. If it doesn't really fit you, I would suggest taking a heat dryer/blower to it and shaping it around your most sturdy slip on till it melds to form. I will suggest that anyone trying out mermaiding for the first time, wear dive socks and practice with just the monofin or bi-fins/ snorkel fins first.

This beast is large and fairly heavy at about 5-10 pounds out of water. Does not come with a carrying back, but would fit inside a beach bag or artist canvas bag. The appeal to me was the eco friendly creation and rubber as opposed to hard plastic like the Finis line has for Pro Free divers. I won't lie, this might cut your skin raw and will induce blistering after prolonged wear. So, be warned and know your limits. It did arrive a bit dusty and one of the tips curled. Added a little heat from a blow dryer, laid a couple books on top, and it was good as new after an hour of cooling. Really, I don't think curled tips will affect the over all performance of this fin.

I'll add a video of it in action in the water as soon as my local watering holes open up.

My daughter loves this fin, but it does start to compress on her feet after awhile. You definitely need fin socks with it because it will rub raw spots on the feet. After I modified her tail skin to fit though this looks beautiful in the water! And this is best for strong swimmers.

Update: I have included pictures of both a modified tail covers and a made from scratch one. The purple one is the made from scratch and is next to a fin fun tail skin and fin. As you can see the Mahina is a lot larger. The blue tails and green are all purchased and then had fabric added beyond that to cover the extra length and width of the Mahina. I loved that we did this because we were able to be creative and create original fabric tails.

Excellent. I'm a shoe size 8.5 and the feet pockets are a little loose, but nothing some 3mm scuba socks couldn't fix. It has fabulous propulsion and looking amazing in the water. I put it in my mermaid tail, and have a short video (linked below) of how it looks in the water. I'm swimming a little awkwardly because I didn't know I was being filmed but it really is a good video of the movement of the fin.

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This is now my favorite fin. I have several monofins and make mermaid costumes often, but I wasn't prepared for how easy this tail would be to swim with. It's a little heavier than other monofins out of the water, but once you're in the water it is a dream to swim with. The extra weight makes it super fast and so you can dive down under water even in the ocean with very little effort. In the pool it is even more effective and actually reduced my time on a 50m by almost a minute. The foot loops are hard to get on when your feet are dry, so my recommendation is to take it into the water, drop it to the bottom, and then put your feet in, or, if you're wearing a tail over the monofin put your feet it and get the inside of the foot sleeves wet first and then put your feet in, close the tail around it, and get into the pool. You cannot walk in this type of fin. The line of the monofin is really elegant though and makes for beautiful tails. It will make you want to spend your life in the water! Great workout too!

This merfin is the coolest thing ever. You really feel like a mermaid and it doesn't hurt your feet. The only thing was they came without the original packing and with a lot of signs of usage. It wasn't new at all. Anyway, I won't return it cuz I love it. And it was used but not damaged. I recommend this fin maybe from another seller.