A small interactive piece that allows resin prints to become part of a liquid motion toy- though it is not considered safe for small children anymore in this version. First iteration I tried, so improvements have already been thought of- please use safely!

Wailmer example file from Gorpi here on Thingiverse https://www.thingiverse.com/thing:4762179

A bottle with some sort of liquid-tight stopper (wide enough opening for 3D print to go into)
3D printed piece (resin in this case)
Food-grade mineral oil
DI water
Zinc chloride or Calcium chloride (if using resin printing)
Food-coloring optional

1. 3D print your desired model
   I printed small Wailmers that would be able to fit in the bottle I chose. I used gray resin and a Mars 3 printer. Then paint them with primer and paint, or skip and use nail polish. Seal with spray or nail polish topcoat.

2. Prepare the water
   In a plastic cup, I added enough Zinc Chloride into DI water to make the density of the water solution greater than the density of a test resin piece. I don't have the exact concentration, just added until the test piece floated nicely. I added a small drop of blue food-coloring to the water solution (adding alcohol inks or nail polish did not work).

3. Assemble
   I poured the water into a glass bottle until halfway, then added the painted Wailmers. Then I added the clear mineral oil until near full. Then I firmly pressed in a matched-size cork stopper, and finally sealed the edges with hot glue.

This is the first I've tried this out, because I wanted a specific liquid motion toy and couldn't find it. My background is chemistry, and I have extensive experience in chemicals and chemical safety- here are my thoughts on improvements:

Use calcium chloride instead of zinc chloride. I only use zinc chloride because it comes in a non-bulk option so I could test the concept. But it is more caustic than calcium chloride and a bit more expensive, too. Either way, this makes it not safe for small children or individuals that don't have the self-control to not drink the liquid should the toy break.

Try using a high-resolution filament printer. I only have a resin printer, so I had to adjust the density of the water to be greater than that of the cured resin. But filament has a variety of different polymers at its disposal, including those that are lighter than water naturally, meaning it will be safe for small children once again. Also if the prints are rubbery, you may be able to squish them into a smaller bottle opening.