on the rocks 意为触礁、毁坏，marriage on the rocks 即为婚姻触礁、夫妻感情破裂。

【例句】
It's said that their marriage is on the rocks.
据说他们的婚姻已经濒于破裂。

It's to say that arguments and rows don't mean that a marriage is on the rocks.
据说争执和吵闹并不意味着婚姻要走到尽头了。