electricity in water

Can a PS generate current into the sump that it is sitting in ? Last night
I was able to put my hand into my sump, now, 8 hours of running time later,
I get a mild, but nonetheless unpleasant shock that does not seem to
discharge or kick my GFCI.

Any ideas ? I don't think troubleshooting this is going to be easy. I guess
I could use a multitester with on probe in the sump, but where would I put
the ground ? If the voltage was being caused by a regular electrical short
then the GFCI should have tripped but it did not. So, where do I put the
ground from the voltmeter ?