Biogalleas and Tachynas

Two members of an Alien fauna on a fictional Earth-like Planet called Snaiad.

The Prownose Heartwhale's Description from the website:

"These large Cardiocetes are usually heard rather than seen underwater with their throbbing jet-beats reverberating across the waves. While they superficially look like the Monocardiac giants of the north, the construction of their mouths, multiple jet-hearts and even their feeding strategies set them apart as Polycardiac Cardiocetes, albeit huge and filter-feeding ones. Their filter-feeding is more like taking bites out of the giant plankton swarms, rather than passively swimming through them like their Monocardiac cousins. They have also secondarily tuned down the engine-like multiple jet-hearts of their lineage, pumping along at a leisurely pace instead of the jet-ski-like frenzy of their smaller relatives.

This species is readily identifiable through its tapering, ram-like snout extension, used in a variety of social activities such as friendly snout-rubbing with members of the same pod, sexual displays for potential mates, and outright ramming against intruders or rowdy males. There are at least four separate species of Biogalleas in Snaiadi oceans, with one, B. polaris, also widespread in the Northern Hemisphere."

The "Swordfish's" description from the website:

"Not all Polycardiac Cardiocetes are sluggish giants like Biogalleas. In fact, most Polycardiacs are comparatively small species, living more like aquatic swallows to fuel their energy-hungry metabolisms. The thirty-plus species of Tachynas are fast, pelagic predators feeding on small swimming organisms such as Swimming Centipedes and Sea Serpents. They all have six jet-hearts arranged along their jet tracts like engine cylinders, pumping out water at a frenzied pace. With this propulsion mechanism, they are among the fastest swimmers observed on almost any human-inhabited planet. They frequently use their jets to leap clean out of water, perform amazing acrobatics in air or under the sea, and chase their prey with an astonishing agility. All this, however, come with a price. The huge energy expended on their jet propulsion means they must continually battle starvation, and their hyper-charged metabolism leaves them with life spans much shorter than aquatic creatures of similar size.

It has recently been observed that some Tachynas species, including T. tachyno, perform a limited form of supercavitation, leaping out of the water and splashing back in with a moving bubble of air projected in front of their faces. These bubbles, maintained in place by the hydrodynamic properties of the grooves along their long beaks, surround their faces like diving masks and enable them to move even faster underwater."