Once upon a time, a number of adventurous scientists moved out from the known terrain of scientific literature to explore the terrain of science related story writing and storytelling. They aimed to create short stories, which address the current threats our oceans undergo due to "human-made" climate change, contamination and exploitation. The first part of the adventure is now completed. The imagination formed into words and several illustrators took a step further to transform words into images. We present before you these adventures and invite you to sail with us. "Once Upon a Time... a Scientific Fairy Tale. Volume I", is an anthology of nine stories, two poems and one sustainable lifestyle guide. This is the first result of a collaborative effort of 29 scientists (the "Once Upon a Time-team", OUAT-team) and the professional support of several artists. The protagonist of the stories and poems are marine and terrestrial animals, grown-ups and youngsters, people like you and us.