Sometimes in Classic Who you find the longer serials (or to be fair, any serials) don't have enough plot to fill their time. I'm so glad The Sea Devils is not one of those

I liked the plot and the acting, the Sea Devil costumes are charming, and the location filming was enthralling (shout out to the sea <3). The Doctor had a sword fight with the Master, stole his sandwich, and then stole Jo's sandwich too. What more do you want from Doctor Who