Can you please help me solve this lab:

Question

Design an item no bigger than a 35 mm film conatiner that will float at the 400 ml mark in a 1000 mL graduated cyllinder with 800 mL of water in it. The item can only be made from "trash", recycled items and common household goods like paper clips, rubber bands, ziplock bags, balloons, etc.

I've tried a lot of things, but can't think of any household items that have densities that would cause them to do that. Please help!

There may be an easier way to do it but I think this will work. Add a handful of paper clips to a rubber balloon. With a series of trials, you can add more paper clips, remove paper clips, and inflate the balloon to vaious sizes to arrive at the right "mix" of paper clips and inflation.

Thanks for responding!
I'm trying to perfect the balloon technique, but it's hard. Does anyone else have other ideas on how to make this work? Other than the balloons I've tried putting things like paper clips, staples, beads, etc. in the film container so the container will float and the other material will make it sink, but I've tried for hours and it's hard to perfect these. Any other suggestions?