I saw this idea at my daughter's house. It was a bigger bottle, and swirls of fine glitter. I saw several blogs that showed how to do this. I explored it on Pinterest:
Anyway I just experimented. I have some perler beads, but they didn't work because they floated. I found some other beads that sank as well as some small gems. I used the glitter I had, some from my mother in law. In the jar on the left, there's large green glitter, medium pink and tiny clear snow glitter. The water ended up tinted pink. When you shake it, it's dark green, which gradually changes to blue (?) then pink. I stuck a few things in there but they are hard to see. I did discover that some of them sank in just water but floated when I added the glycerin. I'm thinking some tiny plastic creatures would be good but I don't have any at the moment.
The other one has red glitter in two sizes as well as gems and a few beads.
I used mostly water and added glycerin until I liked the way it floated. I think it ended up 2/3 water and 1/3 glycerin. There's all kinds of recipes to explore.
This one for today is my favorite. I started it with black sand and I hated it. So I strained out the sand, found Grandma's gold glitter from way back... and added some ultra fine gold, and a little multi color ultra fine. I scrounged around for shells and found enough. A drop of liquid watercolor in blue... a bit of glycerin to slow it down... and yes I love it. Here's a closeup. Now to work on lid glue. Saw one blog that used duct tape. I have some pretties so might do that.
I ended up gluing AND taping. Gave to Baby M. She loved them. I still have the shell one, I needed one for me. Am going to make some more for the Other Babies. I think Baby C. would love them. And then there are still two Unborn Babies coming up.....