From their website :"Fuel can absorb moisture from the atmosphere - even more so with the addition of ethanol. Crank case oil can also become easily contaminated with moisture. Sea Foam® fully encapsulates the water molecules in the fuel and oil to prevent phase separation - rendering the absorbed moisture harmless."

Also:
What is it about Sea Foam® that makes it so safe to use?
Sea Foam® is composed solely of three specially blended petroleum oils – each having specific functions such as lubricating, cleaning or moisture control. There are no other chemicals (not even color dyes) included in the formulation. Being of the same basic petroleum chemistry as the motor oils and gasoline you already use in your engine, Sea Foam® is completely compatible with all engine components, fuels, lubricants and other additives you may have in your engine. Sea Foam® will not damage gaskets or seals, and will not interact in a negative way with motor oil or fuel, or the additives used in them"

I emailed them to ask specifically about this question. I'll post what they reply with.