Most people know about the famous Starbuck’s mermaid and her bizarre two tails. enter image description here Starbuck's Logo

However, few know that her origins actually harken back to very old depictions of mermaids that can be traced back to Ancient Rome and Greece. A particularly famous two-tailed mer-creature was Melusine of French lore.

All that said, I’m working on an idea where instead of the classic single tail, my merfolk took Melusine’s path. And I was curious— how fast and efficient would this set up be for overall movement? I recall answers in other questions,

How should I create my Merfolks to make them landbased?

have a mermaid push her legs together to form one tail, but I was wondering if a scuba diver’s “kicking” method could also work in the long run?

Would this make it difficult or easy for them to traverse on land too? Or would it be fine for them since they’d technically be “bipedal”?

For the sake of answers:

My “merfolk” are humanoids that are highly adapted for aquatic life but aren’t completely bound to their watery habitats, so they’re more amphibious than others, aided by primitive technology. Let’s say the “merfolk” are, on average, a total of 12 feet tall/long, with their tail/legs taking approx. 50-55% of their length, and outstretched feet taking around 10-15%. They have fake, removable fins (like human divers) that can add whatever extra length or shape they need for swimming.

(Adjustments for more efficient numbers are allowed, I’m just spitballing here.)

Thus, at first glance, the overall structure of the legs seem fairly similar to humans where they join the body like hips and move up and down when swimming. However, they can become way more flexible towards the end. When they’re pressed together, they have the ability to allow the swimmer to move similar to other sea creatures. Some can move in stiff but strong motions like sea mammals such as dolphins, others are more “loose” like moray eels (but in an up-and-down motion). They can swap between "mono-tail" and "two-tail" forms when needed with practiced ease.

What I’m looking for in an answer:

  • Practicality, or lack there of, of such a form in terms of swimming and walking, as this race is amphibious. Detailed pros and cons please.

Edit: I’m leaning more towards the water side of “amphibious”, so I don’t expect them to be marathon runners or anything on land. At best, they’re a little lacking in balance and may require canes and such, if not flat out wheelchairs for those who are really lacking practice.

  • $\begingroup$ Please remember to ask one question per post. If you want to know the tradeoffs between split and mono fins for swimming and walking that's one question. Don't ask additional follow up questions. Don't ask which approach your mermaids will choose. In world choices are not appropriate questions for this site. $\endgroup$
    – sphennings
    Commented Jan 8 at 20:35
  • 1
    $\begingroup$ I'm not asking which they'd choose, I'm asking the practicality of the anatomy I suggested for both land and sea, since the merfolk in question are amphibious. $\endgroup$ Commented Jan 8 at 20:37
  • $\begingroup$ You say "Should they take this approach" an edit that removes extraneous information and additional questions will make the intent of your post clearer, and resolve it's issue with asking multiple questions. $\endgroup$
    – sphennings
    Commented Jan 8 at 20:43
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    $\begingroup$ @sphennings A little odd that someone would be hung up on that, but I edited it. Is it better? $\endgroup$ Commented Jan 8 at 20:46
  • $\begingroup$ You're still asking two questions at the bottom of your post. On a stylistic level I'd recommend cutting your post down for clarity. Adding 1 image may be helpful but 3 hinders the readability of the post. Please remember that unlike other question and answer sites we're rather restrictive about the sort of questions that can be asked. Your post was on the cusp so I decided to suggest edits, instead of voting to close. $\endgroup$
    – sphennings
    Commented Jan 8 at 20:53

2 Answers 2


All you're describing is a basically a scuba diver. Sub par in the water compared to aquatic animals and ok on land.

Both a fin on each leg and a single one for both are used already by divers. A mono fin is a very efficient way of swimming underwater where you undulate like a dolphin.

There are various sorts of fins that all have their own use cases. These include split fins, paddle fins, mono fins and even hand fins.

  • $\begingroup$ Kind ooooof…but that is intentional though. They’re amphibious, but not expected to dwell for long on land, in fact clumsiness is expected for those not accustomed to walking. I thought the added flexibility might be a boon that aids them more while still allowing bipedal walking to a degree. I’ll add that info to the post. $\endgroup$ Commented Jan 9 at 1:52
  • $\begingroup$ @Thunderhammer to be anything better than a scuba diver in the water you need to streamline them somehow, it's the resistance that is the major limiting factor if you ever do any diving, and strength, but mostly resistance. $\endgroup$
    – Kilisi
    Commented Jan 9 at 2:13
  • $\begingroup$ I’m aware of that as well, but I was curious if altering the legs could make a speedier or more efficient movement. A sort of best of both worlds kind of thing. $\endgroup$ Commented Jan 9 at 2:19
  • $\begingroup$ You could turn the ankles and get rid of the heel perhaps so the toes point straight down, that would make a nice difference in the water and make them clumsy on land. They'd basically tip toe everywhere instead of stride, could run I guess but not for long or easily. $\endgroup$
    – Kilisi
    Commented Jan 9 at 2:23
  • $\begingroup$ Interesting. 🤔 I considered that at some point but wasn’t too sure. $\endgroup$ Commented Jan 9 at 2:26

Melusine-like merfolk would be like, super fast and agile swimmers, but they'd have a tough time walking on land.

They'd have two tails, which would be great for swimming, but not so great for walking. They could switch between having one tail or two tails, which would be helpful in different situations. But even with one tail, they'd probably need canes or wheelchairs to get around on land.

The size of the merfolk and where they lived would also affect how well they could walk on land. Bigger merfolk would have a harder time than smaller merfolk, and merfolk who lived in shallow water or near beaches would have an easier time than merfolk who lived in deep water or far from shore.

Overall, Melusine-like merfolk would be really good at swimming, but they'd have a hard time walking on land. They'd need to use primitive technology, like canes or wheelchairs, to help them get around.

But hey, at least they'd be able to swim really fast and do cool tricks in the water!


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