They are absolutely smart and dexterous enough.

That’s a good point about the sea corroding everything though, they’d have to move to land for industry.

It would start with farming. They already use tools, building fish and mollusc farms would be a likely start.

They can scurry across land in short bursts already. Bringing salt so they can explore freshwater streams and rivers seems possible. Digging canals they can travel in up further into the land seems possible.