Taking into account the novel (which it would be criminal not to) this is clearly a good few months after The Curse of Peladon which happened at the same time. It would explain why the Master is so ingrained at this new prison (which is also mentioned in the novel). I love the fact that he's managed to wriggle himself into a similar position as the one we previously saw. Once again the entire staff wait on him rather than guarding him.
However, once we get past that, this basically turns into another rerun of Terror of the Autons. By which I mean it’s a remake of the villains’ previous appearance with the Master taking over the central plot. Which is a great shame because I believe that the Silurians have a lot more to offer Who. Even their return in New Who in The Hungry Earth/Cold Blood plays practically the same plot with the added benefit of 38 years so the public forgot and much better special effects. We might get Vastra a year later, but she’s a one-off, a fantastic character nonetheless, but not doing anything interesting with the race as a whole. It might be intriguing to see how Clara, someone very offay with Vastra, deals in a proper Silurian plot.
So without the Silurians - which is how I’m referring to them despite their aquatic nature, The Doctor makes it quite clear they’re the same race and the only difference is because the production crew wanted to do an underwater story- what do we have? A return to the standard Pertwee story. Sort of.
First we had a non-Unit story with The Curse of Peladon. Then we had a totally UNIT story with no Doctor in The Face of the Enemy. Now we seem to have a UNIT story without UNIT.
This may seem a little strange, but it does actually help the serial. Alongside UNIT and the Brigadier, the Doctor says aliens and everyone jumps into action. Even if that week’s bureaucrat don’t believe, UNIT is there to make sure they do what’s needed. It removes an obstacle that shouldn't always be removed. By having this as the Royal Navy and giving Captain Hart the usual Brig role the Doctor spends a lot of this serial fighting against authority as well as the Master. Which is exactly what this serial needed to keep it interesting.
Not that the shift to Master is bad. I’m not sure but this also might be where it’s revealed that the Master and the Doctor are old school buddies. Even if it's not this is the earliest I've seen the show use that to its maximum. The serial starts with Jo and the Doctor heading to the Master's prison to check up on him. But while Jo is clearly still in the “this man is evil” thinking, the Doctor's attitude comes across more as he is checking up on an old friend, or even that he's a bit lonely being stuck here on Earth with the humans, and his recent trip off-world prompted him to go see his old friend.
Numerous times the two of them are hanging out, having proper chats between squaring off when shit gets serious. It’s a side of the Master/Doctor relationship that practically disappears when Anthony Ainley takes over. New Who brought it back a little, with Simm’s death scene (both of them) and the sex change and the reveal that Missy’s feelings go a little deeper.
On the other side of the coin. This is perhaps the first time I've seen the full-on action stuff that Pertwee gets accused of so often. The sixth episode is basically a protracted fight between the Royal Navy and the Silurians and the Doctor gets a bit fighty a couple of times, even jumping in to help the odd sailor. Then there's the sword fight. After one of their chats, the Doctor and the Master have a big old fencing match, no holds barred. Unbelievably it's used, in full, in two episodes. Episode two ends with it, and the next episode shows it again. I’ve often wondered (and I know some exist) how well you could edit Classic Who into a shorter format for today’s audience. Just knocking that repeat fight out would get you five minutes back without even trying.
Not to miss out, Jo does a pretty decent job for the first half of this serial sneaking about and infiltrating places. All that talk of being a proper UNIT agent is starting to show again. Things look like they’re about to fall apart as she’s gets all screamy when the Doctor goes underwater, but during the final battle she’s off piloting a hovercraft.
At the start I compared this to Terror of the Autons, but The Sea Devils manages the retelling with the Master far better than the previous attempt. As with most six parters, it could easily trim a bit an episode off and not lose anything, but it’s a pretty decent serial. One that shows that having the Doctor be a regular part of UNIT might have been interesting, but it’s not the best setting for the show. After this and The Curse of Peladon it’s no surprise that this season ended with The Three Doctors and Pertwee given control of the TARDIS once more.