I had an idea. Since I have no gloss paints or anything, to simply squeeze a tube of plastic glue over the top of the blue paint. It always seems to look shiny when it has set, so I thought it might come up as a hard reflective coat on top of the water. Anyway, here's what it looks like when the glue is wet. I'll have to wait for it to dry now and see what happens! Hopefully it will still have a 'wet' look about it when it has dried out.