Which does mean the water content of the fuel you buy has increased, ethanol holds it's own weight/mass in water ... hence the rusting of tank bases ... the expanding fuel tanks ... rotting rubber ... additional corrosion ... decreased MPG ... decreased power output and all the rest of the goodness that accompanies it.
Which is also water at (todays local best price) £1:20 a litre
Seal the tank before it looks like a pregnant elephant