Baby flukes??

Hi,

Tonight I have been passing what looks like little bitty flukes, light brown/tan
color. some are about the size as a pencil eraser, some smaller. Some are oval, some round. A few were round with a tail! they float on top of the water.

These aren't stones because I poked some of them with a straw and they feel more
like flukes or parasites.

What do you think? What are they?

I have passed about 50 of them tonight.

Thanks,
Jessina