This serial has, in the ending credits for each episode, a thank you note to the Royal Navy. I think I see why in episodes like this one where it looks like there were scenes actually filmed on working naval vessels.
But that’s only one small facet of this episode. I mean, a lot happens here. The last episode ended with the Doctor and Jo surrounded by prison guards on one side of the beach, more guards with Col. Trenchard and the Master on the cliff above, a Sea Devil coming out of the ocean in front of them, and a mine field off to the other side. Which way will they go?
Well, through the mine field, actually. And it turns out the Doctor has a device on his person that can detect mines, so that really isn’t much of an obstacle. It helps that the sea monster man starts off by using a ray gun on some of the prison guards on the beach before the Master fine-tunes the communicator enough to get the Sea Devil to follow the Doctor and Jo into the mine field, at which point the Doctor adjusts his gizmo and makes the mines around the Sea Devil explode, forcing the gill man back into the ocean.
Really, why was a mine field presented as any kind of obstacle?
In the end, the Doctor and Jo somewhat easily dodge patrols long enough to get back to Captain Hart at the Naval Base. And he’s worried enough because he lost Young Maester Luwin onboard the world’s roomiest submarine.
I’ve been inside a submarine in my life (it was a museum), and they don’t offer that much room to move around.
Moot point, as the sub was taken over by a Sea Devil and seems to be forcing the crew to go…somewhere.
Back at the prison, Trenchard seems to have finally figured out the Master lied to him, even if the Master offers the compelling reason of Trenchard wouldn’t have believed the truth anyway. Moot point as the Master uses his communication device to call the Sea Devils to invade the prison and pull him out. Trenchard and the guards all seem to die, but Trenchard takes at least one of the Devils with him from the looks of things. So, unlike many weird monsters on Doctor Who, these things aren’t bulletproof. Now, if only the humans on the show had better aim…
Well, this is all fun, and the Doctor isn’t surprised to see the carnage at the prison when he comes back with an armed patrol. The only thing to do is take a look at the sea floor near the prison, and that means doing some diving in a special diving unit like the Royal Navy uses, and the Doctor will do that alone because A) of course he will and B) he can because he’s obviously a skilled diver so C) Captain Hart will do like many authority figures have in the past by no longer arguing with the Doctor and letting the one guy who always seems to know what’s happening do whatever it is he’s going to do anyway.
So, down the Doctor goes, and he’s in contact with the ship on the water’s surface until he gets to the bottom and sees a Sea Devil out his lone window. And with the communication cut off, Hart orders the diving bell brought up…only to find it completely empty.
That could be a problem.