Wiktionary
sink like a stone
vb. (context simile English) To completely fail.
Usage examples of "sink like a stone".
For a while he simply clung to a thwart, fearful that they would flip over at any moment, and he in his armor would sink like a stone.
I'll sink like a stone and be long drowned before I can get a tenth of this scrap iron off me.
The explosive will blow a hole in the hull and the ship will sink like a stone.