﴿ فَٱنتَقَمْنَا مِنْهُمْ فَأَغْرَقْنَٰهُمْ فِى ٱلْيَمِّ بِأَنَّهُمْ كَذَّبُوا۟ بِـَٔايَٰتِنَا وَكَانُوا۟ عَنْهَا غَٰفِلِينَ ﴾

“And so We inflicted Our retribution on them, and caused them to drown in the sea, because they had given the lie to Our messages and had been heedless of them;”

So We exacted retribution from them and therefore We drowned them in the sea al-yamm denotes salty waters for the reason that they denied Our signs and were heedless of them not reflecting upon them.