One of the better episodes so far, though the techno-babble is still hopelessly outdated to modern ears.
Blocking out microwaves by means of a sonar... Sure.
Anyway, Mark's arch nemesis, the evil scientist Mr Schubert we first met in the pilot episode, is back. He uses a huge device that emits microwaves to melt part of the polar caps and promises the US government to reverse the resulting floods if they 'give him' Mark Harris, so he can perform genetic tests on him and create a new race of water-breathing humans.
This is the first episode in which Mark expresses feeling distant from humans, he wants to experience emotions. A theme which would come up again in future episodes.