How would living underwater affect aging?

[malinghi]

If it were possible to live underwater, how do you think that would affect aging? I feel like many of the things that contribute to physical signs of aging would be reduced if you lived underwater, like the sun's effect on skin. It also seems like there would be less wear on joints, and elderly people would not be at risk of hurting themselves from a fall. What do you think? Assume there's no threat or predators or starvation (same as for people living in any developed country on land). Do you think the average lifespan would be extended, and if so, by how much?

[Mermaid Jaffa]

Do you mean underwater in air filled homes? Or underwater with gills?

[malinghi]

I kinda wanted the question to be open ended, but I guess I'm thinking more like mermaids. No breathing apparatus required. I feel like if the question is considered with respect to humans the answer is just going to be that they'd get a vitamin D deficiency, or the bends, freeze to death or some other variation on "humans can't live underwater".

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[Theobromine]

Aging is a biological process. Environmental factors can accelerate aging, but you can't eliminate aging by eliminating all those factors. Almost all known organisms experience senescence (https://en.wikipedia.org/wiki/Senescence), which is essentially the degradation of DNA in the cells after many rounds of cell division. (DNA has long strands of non-coding base pair sequences called telomeres at each end of each chromosome, and during replication, the very end of the telomere gets chopped off by the replication enzymes. Eventually, all of the telomere disappears and the process starts chopping off bits of the DNA that actually code for genes that are necessary for healthy tissue function. The breakdown of these genes is what causes the deterioration that we know as aging.)

That was probably boring. But the point is, you'd have to imagine merfolk as organisms that don't undergo senescence if you don't want them to age at all. Even if you don't do that, I'm not sure that living underwater would extend the lifespan of a human-sized organism that much. It's true that the buoyancy would probably cause less strain on muscles, joints, and organs, but I doubt that would have a significant effect on a creature our size. However, that buoyancy IS what allows, for example, blue whales to grow to a larger size than any land animal ever has. However, land animals can still grow very large (elephants, dinosaurs) before their size is limited by the effects of gravity/pressure.

I'm also curious about the opposite--how deep diving affects the body in the long run. Marine mammals are specifically adapted for depth and time, whereas in humans, the mammalian diving reflex is more vestigial. I haven't really done any research on the long-term effects of extreme depth and pressure on the body, but now I want to. This is an interesting question that you could probably look at from a lot of different directions.

Also, if we're thinking about mermaids who have gills or extended apnea abilities, then we wouldn't need to worry about the long-term effects of breathing compressed air. If you ARE curious about what it would be like to live in air-filled underwater homes (or hotels? cuz that's a thing that is possible) I can do some research when I'm less tired and dig up some interesting articles. I know there has been at least one submerged laboratory facility where researchers were able to live for weeks at a time. Returning to the surface required decompression procedures, that's for sure.

[Mermaid Jaffa]

We won't have wrinkles when we're old. Our scales/skins would turn a different color and shed.

Also, I don't think we'll be human looking. We'd be more fish like or mammal like, with scales all over instead of fish half, woman half like tradition says so.

Our colors would also blend in more with the ocean I think. With shallow water and reef merfolk being a much brighter and variety of colors. Whereas those who live in deeper waters, would look entirely different and have diff characteristics too. Kinda like those fishes that live deep down where there's no light, but when you bring them to the surface, they flounder and die.