Way cool photo, Prouboy!  I agree: freshwater jellyfish; I've heard of them, but never seen 'em.  They sometimes show goodly numbers in late summer and fall, and they are catching zooplankton.  Same food for Intrepid Camper's critters which are colonial bryozoans (another tiny invertebrate, but this one forms large gelatinous masses (see   (You need to Login or Register ).  The lime green forms below that, in Camper's pic, may be freshwater sponges, yet a third phylum of invertebrates!