I wonder if an advanced aquatic species could/would make use of hydrothermal vents to harness the some of the transformative properties of fire. Hydrothermal vents lack the property of mobility, yet have the properties of persistence and predictability.

If one thinks of fire as a common evolutionary ancestor of all human technology; I wonder if there is, in the same sense of fire on land, a branching point of technological evolution in an aquatic society; a branching point that humans do not comprehend, acknowledge, or notice.