Not a flower but would work well there ... Euonymus fortunei 'Emerald 'n' Gold' .. It's one of my favorite euonymus. It is a low grower (under 2') but it does spread up to 3-4' (takes a few years) ... to keep it contained more to a 2' footprint. litterally stab a shovel down through the roots to divide the plant (not quite in half, leave one side bigger). You are NOT supposed to be able to divide it this way, but trust me, you can.
Here's a picture of my newly divided plant in the spring... it's along the side of the patio to the right of the water fall (two euonymus seperated by a purple heath). I bought it as either a 2 or 3 gallon pot spring of 2010 ... it was planted in the front yard, and wanted it by the pond. Hubby dug it up and split it. This isnt a plant that can go IN a pond, but does great next to one... Not picky about sun or shade ... it will give you the height to hide the electric outlet and easy to care for (5 minutes hand pruning each year).
Found a picture in my Facebook album of it when I bought it, April, 8, 2010, so attached it.