In her contribution to the “Ways of Water” series, marine environmental historian Hayley Brazier invites readers to explore ocean “ooze,” the complex and mysterious content of layers of the ocean floor. Delving into the history of ooze-related discourse, she draws together the interests of a wide range of audiences in the question of the murky depths, from science fiction writers to telegraph cable engineers. In bringing the substance of the ocean floor more to light, Brazier encourages us to reflect on how we define unknown or less visible spaces on the planet as alien, and what might be the stakes of that process.