Antonyms for the phrase "plunges ahead" would be words or phrases that connote a sense of hesitation or slowness. These may include "hesitates," "pauses," "delays," "stops," "retreats," or "backtracks." Alternately, words like "meanders," "wanders," "ambles," or "drifts" imply a less targeted or focused approach. While plunging ahead often connotes a confident, proactive stance, its antonyms suggest a lack of clarity, purpose, or direction. Other antonyms might more specifically include words like "reverses direction" or "changes course," implying a significant shift in strategy or intention.