I love Waters of Mars like few other Doctor Who stories. I wouldn't necessarily want every Doctor Who to be like this, in fact, its uniqueness is what makes it be so special.

From our first little taste of the peak "Time Lord Victorious" to the sinister monsters (whose effects and performances by those infected are so well done) there isn't a part of this episode I don't like. Even little things like the simple set-up and payoff of the little gadget robot all worked to make this an effective and captivating piece of science fiction. It's dark, full of ideas, and properly explored from start to finish. Easily one of my favourite David Tennant stories, I would consider it right up there with other spooky outings like Blink and Midnight. For whatever reason, it feels like Waters of Mars doesn't quite get the same level of hype, but I think it should. The virus in this story is so creepy. We briefly get a sense of its perspective when it is "talking" through the captured woman, before it reveals itself, but that's our only real glimpse into their thoughts or perspective. Otherwise we are just left with the creepy reality they instill.

Water is patient... that, and how quickly/suddenly the infection spreads, really sticks with me. And it is all capped off with some of the most interesting character work around the Doctor I've ever seen. The stuff at the end with him and Adelaide is haunting. I really like the full cast here. There's just enough personality and pluck to them you really feel bad once the bodies start piling up, and why it is so hard for the Doctor to let history play out. This could have just been a goofy horror episode to close out Tennant's run. Instead, it left me incredibly emotionally invested.

Maybe not every Doctor Who episode can be this dark or push the character this much, but it absolutely should set the standard in terms of creativity and ambition.