n. 25B6; verb
people were floundering in the water : STRUGGLE, thrash, flail, twist and turn, splash, stagger, stumble, reel, lurch, blunder, squirm, writhe.
she floundered, not knowing quite what to say : STRUGGLE MENTALLY, be out of one's depth, have difficulty, be confounded, be confused; informal scratch one's head, be flummoxed, be clueless, be foxed, be fazed, be floored, be beaten.
more firms are floundering : STRUGGLE FINANCIALLY, be in dire straits, face financial ruin, be in difficulties, face bankruptcy/insolvency.
prosper.