The short answer to your question, Angelica, is yes, underwater, current-driven turbines are possible. What I can't tell you at the moment is the potential scale of this energy. If your civil engineer was using the word "we" in the sense of "Taiwan", then I'd imagine the potential is pretty considerable. If "we" meant "humanity", then we might need to be a bit more modest. Not all of us are island nations, after all.
Frankly, in Taiwan's case I think the real limiting factor on the potential of Taiwan's ocean resources is less technical and more political.
And yes, I ALWAYS want to hyperlink in so-called "real-world" conversations. It's less of a problem, though, since most of the people I talk to read my blog semi-regularly.
Oh, and don't knock those of us with the "giant underwater construction" bug. We're protective of our own.