They're a colony of animals living together in fresh water. They're filter feeders that consume suspended materials in the water, so they help maintain good water clarity. Nature IS amazing!
Up close, the textured surface is quite magnificent. I've just read that those rosette-like features are actually groups of 12-18 individual zooids. (https://wmap.blogs.delaware.gov/2018/12/01/delawares-most-famous-freshwater-bryozoan/)
I think these little groups look like colorful stars in a tightly packed galaxy!
I picked this particular blob up because one side seemed to be smooth, and I could see the plant stem to which it had become attached. It intrigued me enough to overcome my hesitation, but I did have to wash slime off my hands afterwards.