I suppose you could take the line that they failed to adapt to live comfortably on land before their technology rendered further physical adaptation unnecessary, but that would be for narrative reasons and not scientific ones. It does not take long to realize that industrialization requires further and further concessions to dry living. One narrative device for making this happen was the relative lack of planetary dry land in the case of the amphibious aliens of the Lensman series. One stand-alone that was later retconned into the lensman universe features amphibious aliens of highly developed technology, who inhabit a planet with virtually no landmass and most of the resources still ocean-derived. Why a species would become amphibious in such a case is not clear, and their amphibious nature was simply necessary to a narrative that they were spacefaring, by all appearances. Their driving goal for spacefaring is actually the acquisition of common metal, iron specifically.

If you want a mechanic for an oceanic species to develop industry, then I think I’ve given a viable and even unique option. That’s extraordinarily rare in sci-fi: to have a truly new premise. But someone has probably already done it right? Anyway, the best sci-fi has a story to tell, and the sci-fi aspect is just a wrapper for the skilled writer. What unique and worthwhile story does this oceanic species bring about? They can’t have chemistry or metallurgy without a relatively non reactive and non conductive environment, we have that arising “naturally” without leaving the ocean. What will they do with it?