Grahame, Lots of positives here. The collision looks cool, the black BG really makes it pop, the purple/magenta is a nice color, The ring of the "umbrella" has a neat lacing effect. You did a great job with this. They are not easy and you need to produce many stinkers to get a keeper-kinda like blurs. I love these water drop images and I look forward to seeing more.
It may be a bit tight in the frame, I would evict the two purple dots on the left bottom of umbrella, maybe a tad sharper.