To flounder is (1) to struggle or move with difficulty, as in mud; or (2) to behave awkwardly or make mistakes. One who flounders does not fail completely but merely struggles. To founder is (1) to cave in, (2) to sink below the water, (3) to fail utterly, or (4) to go lame. While to flounder is merely to struggle, foundering usually involves utter failure.
Because there are degrees of struggle and failure, and because failure is often the outcome of struggle, flounder and founder often come close together. In sports, for example, a losing season can be seen as either a struggle or a failure, and indeed flounder and founder both commonly appear in reference to losing sports teams.
Of course, both words have noun senses that are unrelated to the verb senses. A flounder is a type of fish, and a founder is someone who founds something. As far as we know, the words are not mixed up in these senses.
His progress in creating a more moderate image will flounder if, as expected tomorrow night, he proposes more and more spending. [Washington Post]
If the Eagles flounder next year, especially on defense, look for more eyebrows to be raised at this puzzling move. [Delaware County Daily Times]
Parallel to this is the fact that the so-called peace process continues to flounder. [Jerusalem Post]
Last week, in the latest move to right BSC’s foundering financial ship, the school’s board of trustees pledged to raise money to make up the gap. [The Birmingham News]
These programs make so much sense that a bill extending all three passed the House on Dec. 15 on a voice vote, only to founder in the Senate. [New York Times]