One of my mermaids is on land in the daytime, and I'm just wondering what the sudden existence of sunlight and Florida heat might feel like for her, since she's from the mesopelagic zone and is absolutely not used to anywhere near that level of light and warmth.

Edit: To clarify, my merfolk can develop legs in order to walk on land, and have lungs that are capable of breathing air as well as gills.

  • 2
    $\begingroup$ Mermaid are purely fictional and they are in your world. So they react as you please. Unless you define also her physiology, we cannot answer more than that. $\endgroup$
    – L.Dutch
    Apr 4, 2019 at 14:58
  • $\begingroup$ She would probably not worry about the sun and heat if she's "on land." She'd be too busy drowning. Even if her physiology allows her to breath air, she's never done it before. $\endgroup$
    – Cyn
    Apr 4, 2019 at 15:06
  • $\begingroup$ @L.Dutch Your first part might be strictly true, but one could draw assumptions from how deep-water fish might respond to such conditions, so I don't agree with your conclusion. $\endgroup$
    – Ranger
    Apr 4, 2019 at 15:11
  • $\begingroup$ Do they have; anaerobic respiration and or aerobic respiration, eyelids, irises, thumbs, swim bladders, skin pigment, ears and can they sweat? $\endgroup$ Apr 4, 2019 at 22:16
  • $\begingroup$ Another issue is her perception of movement in space. Probably she would find walking deeply annoying, and will miss the possibility of going up or down with little effort. $\endgroup$ Apr 5, 2019 at 19:14

3 Answers 3


Since you have given us only "the mesopelagic zone" to go on as far as what your mermaid physiology, we will have to make the following assumptions:

  1. The mermaid probably has large sensitive eyes in order to see in the twilight and bioluminescent environment.
  2. The mermaid is not a mammal. (no seashells, sorry)
  3. The mermaid is cold blooded.
  4. The mermaid has gills not lungs. (she probably won't be talking)

With these assumptions in place, the answer to your questions are:

  1. The light in the daytime will blind her. Though she might be able to cope if it is overcast.
  2. The heat will be 20-30 degrees F warmer than the warmest she has experienced in her habitat. And being cold blooded that is a pretty big deal, and will probably cause her to be much more active than she is used to. This may even trigger a manic state.

Other considerations include:

  1. How do her gills stay wet (this is needed for her to "breathe")?
  2. The difference in external pressure, and transition from high pressure to low pressure, has the potential for extreme health problems.
  • 1
    $\begingroup$ "The mermaid probably has large sensitive eyes in order to see in the twilight and bioluminescent environment." Not necessarily. Many whales hunt in the mesopelagic zone, and they rely on sound rather than vision. Whales produce sonar theough an organ called melon, and mermaids have two of those. $\endgroup$ Apr 4, 2019 at 21:53
  • $\begingroup$ @Renan Note that the OP says that the mermaid is from the mesopelagic zone, not that she hunts there. Also note that my answer says "probably", so responding that it is "not necessarily" true and giving an example of an organism which only seldom frequent is argumentative and without valid basis. $\endgroup$
    – Mathaddict
    Apr 9, 2019 at 21:25

Your mermaid does exactly what many of us do, living in Florida. Wear sunglasses, light, loose clothing, and apply sunblock regularly. She is your creation, so you have full flexibility and you've given her almost exactly the same abilities as humans - just a personal touch of not having experienced her ability to see light and breathe air (which she has physiologically - but has not experienced).

(My) assumptions:

  • She is personally unfamiliar with sunlight, walking on two legs, and breathing air; but her species has apparently evolved to tolerate (to some degree) to Florida's heat and sunlight, according to your post;

  • She has access to information and resources upon arrival on the beach? Or at least knows how to survive - it's not far from a lot of great fishing spots, shelter is the sea, weather is normally fine (at least under the water), and in Florida she will not be the weirdest person on the shore - trust me;

  • She has a task to attend to?

Her goal is to trade whatever she brought for clothing and sunblock; dry off, and find who she's supposed to meet in your story. If land-walking is difficult, she should get a mode of transportation like a wheel-chair now that she is using legs and breathing with her lungs.

In essence, she might already be here...

enter image description here


Focusing on the effects of the sun is a good idea but don't overlook pressure differences. The blobfish for example at our pressure looks like a ball of goo but at the depths in the ocean it lives looks much more normal. Perhaps the lack of water pressure has your mermaid similarly bloat and assume a different shape than she is used to.


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