For those who don't understand the theory of why it is required to bond the water:
If you have a plastic lined pool and a two wire appliance is dropped into the pool there would be no path to ground that would trip the GFCI, there has been a few experiments that show this, place a large plastic bucket on the ground and fill it with water plug in a two wire device into a GFCI protected outlet and drop it in, the GFCI will only see a line to neutral load thus not tripping, if you were in that bucket you would be in the voltage gradients and could be electrocuted, now put a grounded piece of metal in the water and the GFCI trips.
Here is a link to a video that Mike Holt produce that explains this:
Mike Holt discusses Stray Voltage
It kind of long but full of very good information, the part of the above is toward the end