freshwater sponge - a bryozoan

Formerly known as "the unidentified blob", possibly a former scifi movie starlet

Floating in an extremely clean lake or river near you.
Near me. Animals living in a colony, filtering water.

Curious for more information, visit this informative website

http://www.umaine.edu/waterresearch/fieldguide/inthewater.htm

Thanks to Anne W. for mystery resolution,