Answer: The aspect of Charybdis that frightened the men was the sound heard.
Explanation:
The aspect of Charybdis which frightens the men more was the sound that the men heard from it. The language of the poet conveys the fearfulness because the men were frightened that they were heading to a big whirlpool which sucks in water.
The crew were so frightened they couod not continue on. The crew has to go towards Scylla or Charybdis in order to live to tell the tale.
