Nectocaris was a free-swimming, predatory or scavenging organism. This lifestyle is reflected in its binomial name: Nectocaris means "swimming shrimp" (from the Ancient Greek νηκτόν, nekton, meaning "swimmer" and καρίς, karis, "shrimp"; πτέρυξ, pteryx, means "wing"). Two morphs are known: a small morph, about an inch long, and a large morph, anatomically identical but around four times longer.