Meaning of “flounder” - Learner’s Dictionary

flounder

verb [ I ] uk us /ˈflaʊndər/
MOVEMENT

to make wild movements with your arms or body, especially because you are trying not to sink

NOT KNOW

to not know what to do or say:

When he resigned, the team was left floundering.
FAIL

If a relationship, organization, or plan flounders, it fails or begins to experience problems:

By 1993 his marriage was floundering.

(Definition of “flounder” from the Cambridge Learner’s Dictionary © Cambridge University Press)