End of the day if its just a few tablespoons full of water it will come out of its own accord after a bit of chugging along, if its in the reason of say half a pint of water then your best draining out most of the petrol and add half a litre of meths in your tank, let it run for a few minutes, dont panic it wont explode or sound like a rocket, you may just get a bit of vapour out of the exhaust pipe, that will be some of the water being burned off.
next change your petrol filter and put in 10 litres of premium fuel, this has additives and other stuff that help lubricate your fuel pump, drive as normal and then put your normal fuel back in once your getting quite low.
advise you drive at least 25 miles with the premium fuel in the tank or just leave the engine running for 30 mins with the heater on to avoid engine overheating
Chemistry, October 2010