Pure water is non-conductive. The purity of water is usually measured by its conductivity/resistivity.
However, put some salt or a drop of acid in there and you get quite a good conductor.
If you have two electrodes in the water, and a current flowing between them, if you put your finger in the water, some current will flow through your finger. Just how much current depends on where your finger is in the water in relation to the electrodes. If your finger is in the direct path between the electrodes, a lot of the current wiil flow through your finger. If your finger is behind one of the electrodes, your finger will pass no current.
This all assumes the the finger is not connected to earth through any other path.
JimB
PS, I feel that you are trolling here with this question. I refuse to believe that you are stupid enough to try it.