Aquatic locomotion
We don't quite know when the first animals and plants evolved, but some guesstimates have been made. Acritarchs are present from about 3200 to 1400 million years ago to the present. That's a wide time-range which means we cannot be sure when they evolved. They seem to have been grazed (eaten) by some early forms of life. Probably some kind of protist developed using existing life forms as food.