Just to widen the scope a bit, in regards to "the development of a sapient, technologically progressing species requires fire, and thus such a phenomenon could not occur under water.", that statement shows a distinct lack of imagination and critical thought. perhaps not a "technologically progressing species" in the same way WE progress, but just a moments thought can give many alternatives. for example, where we progressed thru fire and metallurgy, the hypothetical aquatics may progress thru biological manipulation and electricity. for example, suppose some genius noticed that the shocks give off by an electric eel analogue are transmitted thru a certain species of seaweed analogue, and had the idea of trapping a electric eel and constructing a barrier of said conductive seaweed, where he could connect the eel to the barrier and induce it to give off a shock to ward away a predator. is this not considered "technologically progressing" ? it could lead to genetic manipulation via breeding both eels and seaweed, and looking for other such things like finding and improving a biological source of stronger materials, perhaps based on calcium, silicon, etc to make weapons and devices from. Our own science is just beginning to explore making materials from, for example, inducing bacteria and other "living" organisms to grow them how we want them.