[civilian]

So-- there are caveats. A lot of deep sea life are able to see, and it's because deep sea life also generates their own light. It's a way to communicate to mates, and a way to notice prey, and a way to bait smaller predators.

I also think that echolocation has potential to be equal or better to eyesight! Bats and dolphins do great with it, and I think that it's easy to think of echolocation as being a _visual_ stimuli, even though it's not lightwave-based.

I think the biggest hurdle for an underwater sentient species trying to become more advanced is the difficulties with tool-building. Simple stone tools could be made, but it becomes a lot harder to smelt iron and start doing metal-working.

[LrnByTeach]

I was thinking very same issue for some time. Underwater species will have limitation to advance their Intelligence due to not having access to LAND to make all kind of TOOLS which led to Human Spices advancement . It seems we have a kind of proof at this time planet Earth. 'Long-finned pilot whale' have '37 Billion' Cerebral cortex Neurons , where as Human Spices have 21 Billion .

I think due to their Water environment WHALE did not become the dominant spices on EARTH but Humans became .

https://en.wikipedia.org/wiki/List_of_animals_by_number_of_n...

[civilian]

Yup :)

By the way, the all-caps in your message makes your post kind of confusing, and it almost sounds sarcastic? I'm just letting you know in case English isn't your first language. :)

[outworlder]

On the other hand, imagine the neat tricks they could come up with using magnesium alone.

Would they have to be underwater, though? They could use the sea surface, provided the atmosphere is not toxic to them.

[civilian]

Yeah the sea surface is a glacier. There might be air pockets though? But it would also be near-freezing there, whereas the core would be much warmer, and would also have more pressure.

[36bydesign]

Isn't the surface frozen?