The basic approach here is the same as with the classic drop sculptures, but I create two or more sculptures simultaneously by using several valves. There are two varieties: either side by side, or interacting.
Besides getting the timing right for 2 or more sculptures, the difficulty here is with the interaction between the two sculptures. When two drops collide with the water surface at the same time, the resulting craters interact with each other, which has an effect on the rising columns: often they are tilting one way or the other, and it is really difficult to get two columns that are rising straight and parallel (especially high columns). However, I have managed to achieve this a couple of times, and you can see the results below. If the columns are tilting towards one another, you can try to put another drop on top, which also yields interesting shapes (e.g., "Umbrella For Two" and "Tango").