There's Classics and Archaeology all over this series of Doctor Who - I don't think I've ever seen so many bloggable episodes in one series! (Bearing in mind River is certain to return by the autumn if not before, and we might be seeing Rory the Roman again as well).
This episode had a lot of very promising ingredients for a Doctor Who story - Pirates! Treasure! A Curse! Hugh Bonneville! Rory! Matt Smith continues to grow on me and much of the episode featured a nice, traditional adventure story with a bit of danger, and the TARDIS going missing, which always ratchets up the tension nicely. A few flaws at the end - Rory dying holds no dramatic power whatsoever any more because he's done it more often than Harry Kim and we didn't need the reminders of the Doctor's apparent (and equally drama-free) impending doom and Amy's maybe-pregnancy, because this was a stand-alone story and should, therefore, have stood alone. On the other hand, I'm sure we'll see Captain Avery and his crew again in the future, and I look forward to that, pirates are always good fun. And the Doctor's characteristic dislike of firearms is back to normal after last week's unusual fondess for bottom-kicking, so all's well with the world again.
I blogged about Sirens in general a good while back, when reviewing the Red Dwarf episode 'Psirens'. To sum up; ancient depictions of Sirens often included wings, which never get into modern depictions, and I don't think they became sexy until after their most famous appearance in Homer, though this was a point of some debate. The main difference between this Siren and your classic Sirens was that she functions best in becalmed water, rather than dashing people to their deaths against the rocks, for which I presume rough seas would be more effective; plus, of course, she's entirely well intentioned and not a psychopathic killer at all. This episode does rather make you wonder what other forms Voyager's holographic Doctor could have taken (wonderful as Robert Picardo is in the role). The Doctor kept calling her a mermaid, which was mildly irritating - although Sirens are sometimes depicted as mermaids in later (non-Classical) works, this one definitely had legs.
I rather like the reinvention of the Siren as an essentially benevolent (sort of) force, though the inversion is less dramatic for being a bit too reminiscent of other relatively recent Who episodes (Moffat's own 'The Empty Child/The Doctor Dances', chiefly, and people going poof! but turning out to have been transported, not killed, appeared in 'Bad Wolf'). Her music was nicely ethereal and is one of those things that's really hard to do, like casting Helen of Troy - how do you decide what the most beautiful song in the world sounds like? (I like Ariel's little ditty from The Little Mermaid, myself). The idea that she appeared beautiful and sounded beautiful if you'd been injured, almost like a drug, solved this problem rather nicely, as we could imagine she looked and sounded even more beautiful to those under her influence.
I was less keen on the Doctor's reference to 'folklore' that says the Sirens go after treasure ships. Perhaps there's some post-Classical folklore that has them do so, but Greek Sirens just like to crash ships for the lolz, usually - which in some ways can be more frightening and more interesting, though of course it wouldn't fit this story. Talking of interesting, why did Avery become a pirate? We never did find out. Perhaps he's going to show up again later and explain then, though I would have preferred an explanation here - again, this is supposed to be a stand-alone episode. Russell T Davis had a knack for making episodes feel complete and surprising you by picking up on them again later (the watch from 'Human Nature/The Family of Blood' that reappeared in 'Utopia', for example) but there are so many hanging threads this series nothing really feels complete.
Some major plotholes here (why aren't the Doctor, Amy and Avery put straight in the sickbay? why does CPR have a 100% success rate on TV, when it has a 20% success rate in real life?!) but this was a fun run-around with lovely production values and I'll be quite happy to see Avery and his crew again, as we undoubtedly will. If they bring more Classical creatures with them, so much the better!