water spider

Short definition from Wiktionary

Noun

1. 1
   An aquatic spider; a spider that lives or spends time in or on the surface of the water.
2. 2
   An aquatic spider; a spider that lives or spends time in or on the surface of the water: the diving bell spider.
3. 3
   A water strider, which superficially resembles a spider and lives on the water.
4. 4
   A warehouse worker who performs only certain specific tasks, often replenishment.