Okeanos
Okeanos is the second moon of Jove, and is usually considered the fifth of the seven Earths. He's a little waterworld, just barely big enough to hold onto his atmosphere.
He has no native plants or animals, only a few microbes. Some keep the world warm and breathable by producing methane and oxygen. Some live suspended in the water, others form microbial mats at the surface. Okeanoid life has a unique biochemistry, so it has no nutritional value for humans. But some tastes good enough that it's been put in teas or condiments.
There being no dry land on Okeanos, settlers live on ship - cities or floating islands (typically descended from those of Venus). Many of them are interested in Okeanoid life, but the larger draw is tourism. He's a very popular honeymoon destination for Celish newlyweds! Health tourism is also common, many believe they'll be aided in the low - gravity, pathogen - free environment.