floater

noun

a person or thing that floats
☆ a person who illegally casts a vote at each of several polling places
☆ a person who changes his or her place of residence or work at frequent intervals; drifter; esp., a transient laborer
an employee who works at various times, locations, etc. as required by an employer
an insurance policy covering movable property irrespective of its location at the time of loss
specks that appear to float before the eyes, caused by defects or impurities in the vitreous humor; muscae volitantes

See floater in American Heritage Dictionary 4