The natives of Jupiter's moon Europa are a deep sea eel-like race with goggle eyes, long fins adapted for manipulating tools, and prominent gills. The gill coloration varies among individuals, from pink to blue to bronze. To visit Earth they need to be concealed within pressurized water bags, with opaque walls to prevent sunlight from getting in.
Thousands of years ago, a group of Europan colonists have settled on a subterranean sea in the Elysium region of Mars. They observed Human probes reaching the red planet in the early 21st century and became worried that Humans would claim ownership over it. After contacting the Chirpsithra, a group of them were brought to Earth to discuss the subject with Human authorities. In an improvised trial presided by the Chirps, it was decided that Mars belonged to the Europans, given how humanity had possessed the technology to colonize it for decades yet made practically no attempt to do so.
- Losing Mars, by Larry Niven (2006)