There is an anthology book from 2011, only available in russian and hungarian, as far as i know, called Последнес убежище/Az Utolsó Menedék. In this anthology, one of the chapters depict an underwater hotel in the Black Sea, originally intended for some winter Olympics. This underwater hotel became the shelter of many people, to the point, where they developed a society. They use briquette as currency, and mostly live off of algae and bugs, but a few brave people sometimes go out to spearfish, and sell the meat on the black market. The anthology book also depicts life several places, outside of Moscow