I need an elective and I can't decide between life sci 2H03-Environmental Life science and Earth Science 2WW3-Water any suggestions in terms of how interesting it is and what are the chances of getting a 12 in either of the courses.

For Water, I think it's possible to get an 11/12 in this course. HOWEVER this depends on the teacher. I had John maclachlan. But Bernier is a very good prof too.
But it's important to know that if you're not interested in environmental issues, this course may not be the best electives because it's very memory based. So if you're not interested, you won't be motivated to work hard for this course.

On the positive side, the workload isn't bad at all and the tests are mostly fair except for the random question here or there.