What type of gas? If non-ethanol, yes. Let it separate out, pull the gas off the top and pour it back in the tank.
If you were using fuel that contained ethanol...it's different. Ethanol mixes with water much better than it mixes with gasoline, and any water in the fuel will draw the ethanol out of solution with the gasoline, so what separates out is only gasoline, but of a considerably lower octane grade now that it's lost it's ethanol. If you run the boat on 87, I might add 5 gallons of your recovered fuel to 20 gallons of fresh 91 out of the pump, but aside from that, I'd use it to kill weeds.