I know that it isn't perfect, but for a first time... I am so proud of myself! I must thank Collete from My Simple Little Pleasures for all of her wonderful tutorials. I must say that she the queen of water marbling, IMHO at least. You can check them out on her You Tube page.
When I was working on this manicure I noticed a few things. First, borh work well in the water, Shine especially, but Goth dries more quickly and can leave bald spots when you draw your design. So, I would recommend possibly finding a different black, or letting Shine be your primary color, like Collette did here. If you really want to use these colors as I did, go for it! Just know that you'll have bald spots in your design where you draw your petals and you might struggle to get your flower drawn in time depending on how quickly you work. On my first hand, my left one, I used Shine as my base (like Collette) and you can see the "holes" in my design. In some of the nails I sort of liked the effect, but not all. So on my right hand I used Goth as my base color and LOVED the effect. The colors were bolder and NO bald spots :D It really just depends on the look you want.
So overall: a fun and educational mani!