If I add more acrylic water to a floral arrangement, after it hardens, will it mess it up or look funny?

Well, it doesn't exactly look funny, but what happens is that a line develops between the original application of the acrylic water and the addition you put on top of it. It also depends on the time frame between the first pouring and the second. The longer the time between pourings, the more noticeable the line becomes. If it has been a while, be sure to suck out any dust that accumulates on the first layer because I didn't and that was really noticeable. If you want to add more and don't like the line, you can add a ribbon, gimp, and/or a row of ribbon roses, glued to the vase on the outside to hide the problem. That is what I did and you cannot tell where the differential line is now.