Typical old wives aviation tale.
Adrian has it right. The rest of you seems to prefer to indulge in keeping the old tales going.
Few questions:
Q: How often does your car engine stop due to water contamination as a result of condensation in a non full tank?
A: Never.
Q: Can I fill up an empty metal container with water by leaving it in a hangar for a few days and nights?
a. Yes of course, that is how we fill them anyway!
b. No, are you stupid?
Water in fuel tanks in aeroplanes is a result of dodgy seals or contaminated fuel being put into those tanks.
Nothing more, nothing less.