Sure we can. We can compare the genomes of modern land and sea creatures. We can look for common ancestors, and then ask, from their morphology, whether they lived in the sea.
I do not have a dog in this fight at all. I have two degrees in Math, one in CS and in Philosophy (I do not consider CS to be a "Science" and I do not consider my self a "scientist," but I am using a very precise notion of what "science" is, an notion I might add that precludes much of what we call "science" today.) I have worked with world class physicists, some with Nobels, and have a great deal of professional exposure to science and much interest in it, but that interest is mostly from a formal point of view.
You cannot as a scientist really call this any sort of empirical test. No physicist would claim this "formulation" was anything more than supporting evidence that by inference supports a claim. Clearly, other inferences are possible. You are merely relying on relative plausibility to make your case, which is hardly an empirical test. It the logical, philosophical and methodological senses, I am afraid the IDers have got you here.
It is the nature of the problem, and one of the reasons that the whole endeavor has historically called "Natural Philosophy" until recently, though granted that as genetics advances and edge of this complaint dulls considerable.
But the two points seem to still logically stand: 1) Neither the ID theory or Evolutionist rebuttal to ID is "testable" in the sense that this person from the AGU suggests, and 2) It is therefore specious to claim that one has validity over the other purely on this basis.
My guess is that this is not really what you meant to say, but it is what you seem to be saying.