It's unlikely an aquatic species can achieve technological breakthroughs needed to spread like humans can. It would be very difficult for them to build fires, smelt metal, and create the advances based off of those tools.
While they can be extremely smart and adaptable, it's difficult to imagine how a species like that could develop machines.
Sure, there's possible ways around it, like natural vents and geothermal power, but why would they utilize these resources without a benefit like cooking?
Shells or coral could serve as early tools, but (just my opinion) I feel it's a little human-centric to assume fire and metallurgy are required to progress. Just because we did it that way, doesn't mean another species would have to.
I've spent a lot of time thinking about this exact subject, and I dunno. As much as I consider it, as abstractly as possible, I have considerable difficulty finding an alternate route to significant human-like dominance. Fire and metallurgy are just so incredibly useful across so many domains. I challenge you to present a reasonable alternative route.
Yeah, but we did all of our discoveries as a land-based species. It's totally possible some water-based species would find other crazy useful early techniques, then eventually discover stuff like "fire" much further down the line with access to more robust technologies. Their scientific roadmap would look very different from ours, but there are so many weird tricks and techniques that would eventually lead towards some of the dominating processes we have.
It's totally possible some water-based species would find other crazy useful early techniques
Such as?
Even then, they are still short-lived, non-social animals who don't raise their young. How do individual discoveries compound into robust technologies?
whatever comes after us will have to make due with whatever crap we leave behind. There wont be enough natural resources left for them to use if they want to do anything larger scale or advanced