The oceans would probably not disappear, but the composition of the atmosphere would be somewhat different.

Two major things contribute to this: the mass of the planet and the thermal environment. The mass of the earth determines the escape velocity (how fast you have to go to break free of its gravity). The temperature due to our proximity to the sun determines the thermal distribution (and by relation, the speed) of different gas molecules. If the average thermal velocity of a gas is in excess of the escape velocity of a planet, then we'll see most of that gas eventually escape. This is one of the reasons you don't see a ton of hydrogen gas or helium gas in earth's atmosphere.
Source(s):
http://www.astronomynotes.com/solarsys/s3.htm

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