Wigfrid's lightning spear allows you to clip onto the water

Allight the ability indicator with the shoreline (like shown in the image)

The way you need to allign it is very specific, it is pretty inconsistent and sometimes pushes you onto the shore. But it can clip you out of bounds.(Generally it will work if it is alligned into a sort of a "sweet spot" any cursor movement to the right or the left will dissallow the ability)

After alligning, use the ability, and see the wigfrid walk on the water.