I was really looking forward to this one as there has been only one brush with historical pirates in Doctor Who in the past (The Smugglers). There have been plenty of space pirates (The Space Pirates, The Pirate Planet, Terminus, The Infinite Quest, etc.) but only the one historical. I thought this would be a great opportunity to do some modern pirate style swashbuckling ala The Pirates of the Caribbean. But alas, I was a bit disappointed.
The pirates wound up being a bit castrated as they were unable to shed blood for fear of going to their deaths. It made sense in the context of the story, but didn't satisfy that pirate aggression I was looking forward to.
I was also disappointed to learn the siren wasn't really a menace but rather a medical ships' emergency holodeck hologram. It all seemed a bit odd and contrived to get all these circumstances together so that she appeared to be the siren of legend including her ability to pass through reflections/water, the singing, her beauty, etc.
And the other thing I didn't like was the fact that during the scripting or editing process, one of the pirates vanished without anything happening to him. He was taken by the siren because he's there at the end, but at no point do we see him get taken and that's a bit sloppy in the storytelling department.
On the plus side, we got to see more of Amy and Rory actually being in love and no sign of the love triangle of the previous series. We also got another instance of Rory being Doctor Who's Kenny from South Park. And we got to see Amy kick some ass for a few minutes anyway which has been lacking as of late.
I also liked how the Doctor had to keep modifying his theories as to what was going on as the story progressed. It showed that even though he seems to know what's going on most of the time, he may just be guessing a lot of the time and was good for some comedy spots.
Not a bad story, per se, but one I was disappointed with and my least favorite from the Moff era so far.
List of thirteenth stories for each Doctor from my favorite to least favorite:
1) The Hand of Fear by Bob Baker and Dave Martin
2) Smith and Jones by Russell T. Davies
3) The Mutants by Bob Baker and Dave Martin
4) Fury from the Deep by Victor Pemberton
5) The Curse of the Black Spot by Steve Thompson
6) The King's Demons by Terence Dudley
7) The Web Planet by Bill Strutton