Water in Gas Tank

[jigman90]

I own a 1997 seaswirl 2150 walkaround and I'm having problems with water in the gas tank again! for the 3rd year in a row I've had to have the tank pumped out! I use absord and staybil everytime I fill the tank. this winter I only left 20 gallons of gas in the tank filled it previously and I still had water! I ask my machenic if he thinks I have a leak somewhere and he says no? well what do I do?
this boat does not sit in the water when it is not being used!
I told the wife that next year I'm getting a new seal for the floor hatch and taking it off and having a look at the tank myself does anyone have any suggestions ?