Episode 5 was better than the middle three, but I couldn't exactly call the series good. It had some good (sometimes very good) moments, but overall "inconsistant" is the word that springs to mind. It really did feel like it was written by two different people (it was!) who didn't really communicate with each other very well? More stuff happened in the finale than most of the rest of the series put together, so the interesting parts were very rushed.
By far the worst part was all the shadowy conspiracy stuff: as I noted before it paled in comparison to Torchwood's 'Children of Earth'. I never cared about any of the characters involved in it and I struggle to believe that they were able to come up with a virus that killed 90% of the Fish People when they seemed pretty inept prior to that.
I don't think we saw anywhere near enough of Homo Aqua (haha, funny name) as an actual society either. The best scenes with them where the initial scenes of Salt and Barclay facing off, but we never got a scene just showing the fish people on their own. It's hinted that there was a conspiracy thing going on with them too ("tides within tides" Salt said) but it's not expanded upon in any way. I'm not sure what we're even supposed to think about them coming out of the series? At times it seemed like they just wanted humanity to clean up their act and stop polluting the sea (that's good!) but then at the end it turned out they were melting the ice caps themselves to drown us all (that's bad!) Isn't melting the ice caps the kind of thing they were mad at humanity about? If they really did just want to kill us all, why didn't they just use their incredibly advanced technology to do so?
There was one episode (second or first) where Salt briefly turned male and everyone was shocked for a moment like "did that just happen!" Then it's literally never mentioned again. I, of course, know that some amphibians can change sex ("life, uhh, finds a way") but why did they throw that in then not do anything with it? Seems like surely something Barclay would have talked to her about later.
Seriously again why did no one mention the plastic dumping in episode 2 again after it happened?
So, Barclay gets to be a fish now and that's kind of happy, but what about his human daughter? I suppose he can shout up to her through the toilet or something.
Kate is just like completely insane now? Like there's no way so gets to stay on as head of UNIT, surely?