这句从句（英语）是对的吗?或者怎样能变得更好.

这句从句（英语）是对的吗?或者怎样能变得更好.
Most mariners have a terrible habit which they usually dump their living rubbish into river while shipping contaminates the local water.
大多数船员都有一个坏习惯,就是在他们航行期间,他们喜欢把垃圾就地倾倒,这样会污染当地水质.
怎么修改能便于理解？

这句从句（英语）是对的吗?或者怎样能变得更好.
回答：
A.您的原文：
Most mariners have a terrible habit which they usually dump their living rubbish into river while shipping contaminates the local water.
大多数船员都有一个坏习惯,就是在他们航行期间,他们喜欢把垃圾就地倾倒,这样会污染当地水质.
B.请看对你译文的修改及修改理由：
(a)
which 应改为that：
因为（which X） they usually dump their living rubbish into river while shipping contaminates the local water 是一个同位语从句,而 which不能引导同位语从句!
(b)
river 应改为 rivers,泛指他们随手就倾倒垃圾的河流；
(c)
while shipping 是一时间状语,最好放在全句末尾或放在连词that 之后,不能插在句中；
(d)
while shipping contaminates the local water：此语序只能被看成是一个时间状语从句了,意为：当航行污染污染当地水质的时候--这与您的原文是大相径庭的,对吧?
(e)
这样会污染当地水质：“污染当地水质”的主语是“他们”,还是“垃圾”呢?从你现有的句子看--contaminates v.是单数第三人称,很明显不是指“他们”,应是指“垃圾”,或是指此种乱扔垃圾的行为；所以应改为：
.that while shipping they usually dump their living rubbish into rivers,
which contaminates the local water.
C.
修改后的句子：
Most mariners have a terrible habit that while shipping they usually dump their living rubbish into rivers,which contaminates the local water.
补充说明：
1）在英国英语中,rubbish最常用来表示丢弃的废物,而在美国英语中garbage和trash更为常用,
如：
the smell of rotting garbage (腐烂垃圾的臭味);
She threw the bottle into the trash (她把瓶子扔进了垃圾堆).
garbage和trash 有时也在英国英语中使用,但仅限于非正式语体和比喻用法,
如：
I don't have to listen to this garbage.(我不需要听这些废话)
The book was trash.(这本书简直是垃圾)
改动较多,请勿见怪,欢迎追问!