After many, many failed attempts at water marbling, I've finally achieved success!
Base - Zoya's Petra
Lime - Sinful Colors' Innocent
Blue - Sinful Colors' Aquamarine
Light Purple - Wet n Wild's 203A (no name -- it's a sheer nude, but over Petra it looks light purple)
Here's how to water marble:
Fill a disposable or unwanted cup with filtered, room temperature water.
With polish #1 drop a ball of the polish in the center of the water. If it's going to work the polish will spread on the surface of the water.
Drop a ball of polish #2 in the center of polish #1's spread. Continue this with the rest of the colors you want to use.
[Optional] Drop in polish #1, #2, etc., again so that a pattern of colors form (ex: red, green, blue, red, green, blue).
Take a toothpick or sharpened pencil and drag it in the polish creating the designs you want. Swirl it, drag it across, whatever, just keep in mind that what you're doing will have to fit on a small nail.
Press the nail (sometimes you can do more than one at a time, but start with one) face down on the surface of the water, continue until your nail is fully submerged, and hold it there.
Take your toothpick/pencil and remove the remaining polish on the surface of the water while your nail is still submerged.
Pull your nail out and push everything into place if you can. Voila! You're done!
Plenty of other sites have water marbling tutorials, and I suggest you watch or read a variety of them to prepare yourself before you attempt this, but here are the things that really helped me this time:
-I don't know if this is legit or just user error, but in the past I've used China Glaze, OPI, and Orly and have failed with each. So use the cheap stuff!
-Use filtered, room temperature water.
-Make sure that you use a disposable cup (or one you don't care about anymore), because it will definitely be ruined.
-If you use toothpicks, make sure there are a bunch loose and easy to grab.
-Account for not being able to use your hands for a while, because this is messy.
-To reduce the mess, you may want to cover your fingers in scotch tape.
-Move quick when adding polish to the water and swirling it around. The faster you are between steps, the more cooperative the polish will be.
-Seriously, this is messy:
But when finished, it yields an awesome result. Every nail has its own personality and you never really know what you're going to get on your nail until you pull it out of the water. I'm so glad I never gave up on water marbling because I am loving looking at my nails.