Although this was one of my original ideas, it didn’t work as well as I had hoped. The problem was that I couldn’t put the dye in quick enough and then get back to the camera. The self timer on my camera is like 2 seconds, which wouldn’t make much difference. Anyway, the dye mixed to quickly with the water and then just sunk to the bottom. I think my only options are to either scrap this idea, or find a thicker alternative that may mix less quickly with the water. I was considering oil but quickly realised it wouldn’t mix and would just settle on the top.