What are marine and freshwater organisms that are too small to swim against the current known as?

aren't they the primary ingredient in Crabby Patties?

baymax, He was just being silly! ( I don't like to joke but when I do! I'm gonna always tell y'all! because i don't joke often! or be silly! so I'll let ya know!)

Guillermo Jr., don't you read the answer? obs not!