Have you heard of the idiom
"like they were dragging iron hooks"
What does it mean?
No, I haven't heard that one; and "dragging iron hooks" doesn't seem to google, so it must be quite uncommon.
I would guess that it's a nautical simile: a ship that dragged "iron hooks" behind it would move extremely slowly, if at all.
Another member may have a better idea, though!
All the best,