What proportion of the earths surface is covered by ocean?

The water on the earth occupies 70% of the planet, leaving land to occupy 30%.

http://geography.about.com/library/faq/blqzearthwater.htm

The wet bit.

Two thirds.
I remember that sombody said, "Join the Navy and see the world" they just don't tell you that 2/3's of the world is covered with water.

It's actually 71%
In Earth's solar system, evidence of subsurface ice, ancient valley networks, and even an ancient ocean occurs on the planet Mars. Water ice and perhaps liquid water occur beneath the frozen surfaces of three of Jupiter's moons, although currently none have free surface waters.

But among the planets orbiting the Sun, Earth is clearly the "water planet." Water occurs on its surface as liquid, ice, and gas. Ocean waters now cover nearly 71 percent of Earth's surface, whereas fresh waters in lakes and rivers cover less than 1 percent. Thick ice sheets permanently cover Earth's polar regions and glaciers are widespread in its higher mountains. Water in the form of clouds masks about half of Earth's surface at any time. Volcanic eruptions continually extract water and gases from rocks deep in Earth's interior.
http://www.waterencyclopedia.com/Da-En/Earth-The-Water-Planet.html

About 70%, same as our bodies.

About 70%

It is between 70% and 71%. I think it might be 70.8% but I'm not sure.