I just watched a fantastic TED talk on the world's oceans by Sylvia Earle. Earle has been exploring and studying oceans for 40 years. She speaks eloquently of what we stand to lose if the current trends of unrestrained fishing, pollluting and damage continue.
Also on the subject of water - this chart shows the sources of water, especially fresh water, around the world. It's an eye-opener. There is a shockingly small amount of fresh water. Look at the very large amount of water that comes from glaciers and contemplate how fast they are melting. Very scary stuff!