Bikini Bottom is sheer. I used four thin coats; I could have stopped sooner but wanted to be sure that the staining on my ring finger wouldn't show through (why just that finger stained and not the others I've also used as accent nails recently, I'm not sure; I can't think of a time recently when I had something completely different on that nail only).
The recent release (and my purchase) of Sally Hansen's Barracuda, another milky blue, reminded me of my promise, so I looked through my blues and the closest I saw to Bikini bottom was an older Brucci, Kathy's Baby Blues.
The bottles didn't look that close to each other, but we know appearances behind glass can be deceiving.
This time, the picture in the bottles was born out on the nails; neither the Sally Hansen nor the Brucci could pass for Bikini Bottom. They're both too opaque, even at only two coats compared to the RBL's four. They're also too light and bright. I'm now wondering about using Barracuda as a base for a Bikini Bottom franken. It would need some clear added to make it more sheer, but I'm not sure what other colors I'd need to drop in to get the base color right. Grey maybe? Or green? Let me know in the comments if you've got any ideas for me, either for the franken or other possible dupes for Bikini Bottom.