Ocean Under The Ice

Ocean Under the Ice is the second of four sequels to the science fiction novel Rocheworld by Robert L. Forward (Baen Books, New York, 1990). The other sequels are: Return to Rocheworld, Marooned on Eden, and Rescued from Paradise.
In Ocean Under the Ice, the human explorers of the Barnard Star system and their large, friendly, amoebae-like alien friends, the flouwen, explore an Europa-like moon about the gas-giant Gargantua. They find two bizarre life forms, one living on the ice, and one living in the ocean under the ice, that are as different and yet as related as butterflies and caterpillars.