Which term describes animals that are free to swim through the water column?

The term that describes animals that are free to swim through the water column is "Nekton." Nekton refers to aquatic animals that are capable of moving independently of water currents, typically through their own swimming abilities. These organisms, which include fish, whales, and squid, have adaptations such as fins and streamlined bodies that allow them to actively navigate through the ocean.

In contrast, benthos refers to organisms that live on or near the bottom of the ocean, such as clams and coral. Plankton signifies organisms that drift with ocean currents and do not have the capacity for significant movement on their own; this category includes both phytoplankton (plant-like organisms) and zooplankton (small animals that drift in water). Zooplankton is a subset of plankton and consists specifically of the floating or drifting organisms within that broader category. While zooplankton can refer to animals that are part of the plankton community, it does not encompass the broader range of actively swimming animals represented by nekton.