Little help with water proofing a toy. Sewing Machines Parts and Sales in Los Angeles

I am making a toy that can go in the water. It’s made of the same fabric used in swimwear and filled with Styrofoam balls.

My question is this, I have this really old unused pillow. it has a normal fabric covering but filled with tiny little foam beads. I was thinking of placing this whole “pillow” the insert into the toy.
I am slightly worried about doing this because this will basically be a toy within a toy and won’t dry out as it should.

This toy will be a pool/tub tub it’s not meant to ever go in the dryer. My concern is the pillow inside might get moldy? I can’t cut the bag and just use the stuffing because the filling is micro beads, and I know it will just leak out of MY toy.

So I would like your imput. Should I just go get more of my stuffing or take a chance on the pillow insert?