I can think of 2 cases in movies where someone, while rattling off their qualifications to a skeptical audience, ends with “and I’m never ever sick at sea.” Philip Seymour Hoffman in “Charlie Wilson’s War” a few years ago, and Alec Baldwin in his “I am God” speech in “Malice”, clip here. In neither case is the person claiming any sort of nautical skills, so their resistance to seasickness seems irrelevant. Is that code for something? Is there some other meaning I’m missing - “I don’t panic”? Because I don’t get seasick either, so I’m thinking of writing such a speech for myself, but I want to make sure I’m not claiming something that isn’t true 
Well, it could be a Gilbert and Sullivan joke.
Yes, it’s from Pinafore.
… And I’m never, never sick at Sea!"
What, never?
No, never!
What, never?
Well, hardly ever…
Bingo. And both scenes were written by Aaron Sorkin, a huge G&S dweeb.