Like a stone falling through water.

[shootingstar]

(Nora speaking) ' Well, it's great. And yes, I just thought I'd send a message that, you know, I am out here living my best life. But I miss home after a while.'
Which one?' asked Marcelo, with a quietly cheeky smile. 'I mean, do you feel more at home in london, or LA, or on the Amalfi Coast?'
It semed this was the life where her carbon footprint was the highest.
'I don't know. I suppose I would say London.'
Marcelo took a sharp intake of breath, as if the next question was something he had to swim under. He scratched his beard.
'Okay, but I suppose it must be hard for you, as I know you shared that flat with your brother?'
'Why would it be hard?'
Joanna gave her a curious glance from above her cocktail.
Marcelo looked at her with sentimental fondness. His eyes seemed glazed. 'I mean,' he went on, after a delicate sip of beer, 'your brother was such a big part of your life, such a big part of the band . . .'
Was.
So much dread in such a small word. Like a stone falling through water. (Here Nora is afraid there could be something off with her brother Joe/ added by me).

(The Midnigt Library by Matt Haig, episode The Podcast of Revelations)

What do you associate with the phrasing "like a stone falling through water." Do the English/Americans associate any specific idea with this wording? What does the author intend to express by it. This wording is baffling me.

 

[Skrej]

I guess it's supposed to be a reference to inevitability. The water slows the stone's descent, but it will still eventually hit bottom. She's dreading what she knows is eventually going to happen.