Well, we should probably talk about the music now.
It's certainly the most distinctive part of The Sea Devils (at least as far as these first two episodes are concerned) and that's because, as this is the first Doctor Who score entirely written and created by the BBC's Radiophonic Workshop, composer Malcolm Clarke has decided to make a purely electronic score, using an EMS VCS3 synthesizer. It's monophonic, which means you only get one sound at a time, but you also get a "purer" electronic sound. What this effectively means is that, as this score is a pioneering one in many ways, you get moments where it sounds like 80s synth scores only in 1972, and then moments where it sounds like someone's making random tuneless noises on a computer, and there's no real way to tell which type of moment you're going to get next. It can be a rather challenging score, and it doesn't help that it's occasionally difficult to distinguish the music from the actual sound effects -- which (to digress for a moment) makes Mark Ayers' edited suite from The Sea Devils on Silva Screen's The 50th Anniversary Collection soundtrack all the more impressive.
Everything else we get though feels like typical Pertwee-era Who. After the reptile attack, we pick up a strand last explored in The Dæmons: yes, it's been a little bit, but the Master is back. He appears to be the only inmate of an isolated high-security prison (remember, UNIT caught him at the end of his last story), and the Doctor and Jo go to visit to make sure they're looking after him. Everything seems to be in order, but it turns out that, true to form, the Master has all the staff at the prison under his thumb -- which leads to a moment where the Master requests a television set for the bedroom -- "Colour, of course" -- and then is later happily watching a children's television show called Clangers.65 But the Doctor is more interested in the sinking of ships that Trenchard, governor of the prison, mentions. So when the Royal Navy refuse to help him (and it's a bit striking that it's the Navy and not UNIT in this story), he and Jo go off to investigate on their own, to a fort in the middle of all the reports of sinking ships. While there they encounter a dead mechanic and something coming towards them...
Episode two reveals the something to be the dead mechanic's partner (as played by almost-but-not-quite-Jabba-the-Hutt actor Declan Mulholland, whose scene was cut from the Proper Version of Star Wars before being reinstated with a (not very good) CGI Jabba for the Special Edition), who keeps rambling about "sea devils". It doesn't take long for the Doctor to actually spot one, which looks like a bipedal turtle in, wonderfully, a blue string vest, but it's not willing to talk. After driving it off, the Doctor declares it to be related to the Silurians (and here's where the equally implausible "Eocene" name comes in) and thinks humanity should try and make contact with them. He's in the middle of this argument with Captain Hart at the nearby naval base HMS Seaspite, in fact, when Jo spots the Master, who's there to get some electronic parts. And when the Doctor heads back to the prison to check on the Master, he ends up engaged in a (rather fun) sword fight with him (why there are swords on the wall right outside the Master's room is another matter), which he ends up winning -- but then he doesn't see the Master pull a knife on him...
They're not bad, these two episodes, but they are rather standard for this time in the show's history, and so far there's nothing to make them really stand out (other than the score). Not that that's a bad thing, though, as they're still entertaining enough. The question is more whether the subsequent episodes will maintain interest.
65 And now you know why the John Simm Master is watching Teletubbies in "The Sound of Drums" -- it's an homage to this scene.