Slowly cruising through the shallow seas, a Jetfin searches for food. It quickly approaches a "microbial city", a strange collection of towers built by autotrophic microbial mats. Over time, the microbes mineralized their mats to strengthen them, creating thick towers from compacted sand and debris. The cracks and crevices between the towers conceal all sorts of small creatures, a fact that has not gone unnoticed by the hunting Jetfin.

Using its long, trunk-like jaw, it probes deep into the reef. But there is no food to be found here today. Fortunately, Jetfins are omnivores, and they aren't picky about what they eat. A type of marine tenucaulian, growing in clumps on the roofs of the towers, makes for an ideal snack.

A Jetfin is comparable in size to a Terran Blue Shark. It is not a particularly large creature, but it is nonetheless quite a vicious threat to the smaller denizens of microbial cities.

Jetfins, as their name suggests, move using jet propulsion. On Terra, jet propulsion is used by quite a few marine creatures, most notably the cephalophods. A Terran octopus fills its mantle cavity with water, and then forcefully pushes it out through a tube called the siphon. The force of the water stream pushes the octopus backwards, allowing it to rapidly move through the water. Jetfins have a slightly different form of jet propulsion. They pump water through their body using powerful muscle contractions, which allows for a more efficient movement. This is similar to a technique used by Terran salpae.

An unusual anatomical quirk of the Jetfin is that it has four eyes. In addition to the two on its head, it also has a pair of eyestalks on its trunk. These "trunk eyes" are fairly simple light sensing organs, and are incapable of discerning color. However, they can detect movement, so a Jetfin, patrolling just above the microbial city, can tell whether there are any small creatures hiding in it.