luò shuǐ
to fall into water
to sink
overboard
fig. to degenerate
to sink (into depravity)
to go to the dogs
dǎ luò shuǐ gǒu
lit. to beat a drowning dog (idiom)
fig. to pulverize an (already defeated) enemy
to hit sb when he's down
luò shuǐ gǒu shàng àn
like a dog who fell in the river and climbs out—shaking all over