Free-living copepods have translucent bodies divided into a broad head, a thorax bearing swimming legs and a narrow, limbless abdomen.

The Atlantic range includes the Cape of Good Hope in South Africa, Brazil, Colombia, Belize, the Caribbean, Jamaica and the Gulf of Mexico.

[3] They also form swarms in sunlit patches of water among mangrove roots at the edge of lagoons in the Caribbean where they have reached densities of 90 copepods per ml (0.034 fl oz).

There is an energy cost in maintaining the swarm in a particular location and each individual faces greater competition for food which makes the adaptive value of this behaviour unclear.

[6] In fact, there are few planktivorous fish feeding on this copepod among the mangroves and the main predator is the medusa of the tiny box jellyfish Tripedalia cystophora.