Instead of getting a splicers attention and dragging them to a puddle of water, try this.
In the beginning once you enter Kashmir's Restaurant, go down the stairs and enter the door the splicer is pounding on. Clear the kitchen area and then head back the door you just entered. You will see 2 splicers playing in the water and Atlas will explain that you can shock the water. If you step too far forward they will notice you and start moving to you. Quickly shock the water, it will kill them and your achievement will unlock.
There are plenty more opportunities if you miss your chance here considering there is water everywhere and water conducts electricity (SCIENCE). Be careful where you are standing because you will take shock damage.