"Sea Devils", a Jon Pertwee episode with Jo Grant as the assistant, was unfortunately one of the weaker Pertwee episodes I've seen. A shame as it's the only one I have available from the library which features the original Master, who I remember always enjoying. He's mostly good in this one as well, but the overall story is a bit plodding, takes forever to get started and has a lot of dull bits between the few good scenes. I think part of the problem was that they had the co-operation of the British Navy in the making of this episode, which meant a lot of atypical for DW bits of location shots on the water and naval base, which didn't add much at all. This wasn't helped at all by the director doing a bunch of distracting visual tricks, quick cuts, sudden zooms and such, plus some weird sound effects.
A shame, as there is the hint of a good story in all of this, but it's not at all realized in the production.