I just watched Waters of Mars on iPlayer, and I thought it was great. You know I am so used to not really liking Doctor Who all that much, episode after episode, and that's the first one I've really enjoyed for ages. I thought it was an entirely suitable story for an hour-long SF show, which has to be suitable for the youngest kids, and also has to be quite scary. And it more or less made sense throughout. It didn't piss me off at all. I liked David Tennant going a bit bonkers at the end. In fact i wouldn't have had it any other way. In all - I haven't enjoyed Doctor Who so much for ages, and it was a real old fashioned exciting story.