Other that the possibility of it becoming a galvanic cell if you use dissimilar metals both contacting the water, which would be minimal, and could be eliminated by using similar metals between the build mesh, and the contact, you won't have any electrolysis if only one contact is in the water. There won't be any actual current flow, just an electrostatic charge building up in the insulator between the water and the strip. It's a not uncommon type of homemade capacitor, and it's capacitance varies with the water level.