Worlds of IF Science Fiction, October 1957; Biggle novella SILENCE IS DEADLY (Volume 7, No. 6) Book

When Clarke dealt with science, he was brilliant. When Clarke dealt with sociology and the nature of man as he did in this work, he did not shine so brightly. If you want to know what an atheist thinks mankind could or would be if he could just rid himself of all that cumbersome superstition (aka religion and morality) and also shed all his violent tendencies including the will to power, then you should read "Songs of Distant Earth" because that is the main theme of the work.
You should be warned however that you will be subjected to a portrayal of passionless sexual relationships with essentially no rules within a population of bland characters who lack not only faults like jealousy but also interesting qualities like enthusiasm and ambition.
The bit about them discovering what might be intelligent life in their ocean felt like a nod to the idea of the "Prime Directive" worked in to add a bit more science fiction to what is essentially a handbook on how to achieve utopia by assisting the evolution of the species.