Unknown Water Organism

I recently did an experiment where I took a leaf of lettuce and soaked it in water for ~3 days and then took some of that water and looked at it under my microscope. I found something that looks like it possibly could be some type of organism but I am not familiar with microbiology, so I do not have a clue what it could be.

The image was taken at 1000x magnification and the size of the object is ~40 um in length (in the longest dimension). The image also was taken using the phase contrast view mode.

I attached an image of the organism I am unsure of. I think the black spots are bacteria, but I am unsure what the larger object in the middle. Any help would be appreciated.



If anyone can take a guess at what the large object is I would appreciate it.