Lightoller had a more tangible yardstick - the steep narrow emergency staircase that ran from the Boat Deck all the way down to E Deck. The water was slowly crawling up the stairs, and from time to time Lightoller walked over to the entrance and checked the number of steps it had climbed. He could see very easily, for the lights still gleamed under the pale green water.

—A Night to Remember,
Walter Lord

Which central idea do the details in this passage support?

There are not enough lifeboats on the Titanic.
The passengers are returning to their cabins.
The people on the ship know that time is running out.
The rising water is like a human being on the ship