Coevolution is a process through which two interactive systems mutually influence each other’s development. Midwater research and remotely operated vehicle technology are two such interactive systems, and at the Monterey Bay Aquarium Research Institute they have been coevolving for 30 years. As the technology has matured, the scope, scale, and complexity of the research has also advanced, particularly in such areas as observing animal behavior and in situ experimentation, which were virtually impossible before we gained direct access to the environment. Here we examine midwater research domains and the technologies that enable them: how new instrumentation enables in situ respiration and fluid dynamics measurements; how imaging and data handling systems build data sets that allow long-term analyses of seasonal, episodic, and anthropogenic environmental changes; and how variable ballast and thruster controls have allowed us to make close-up observations and conduct delicate experimental manipulations without disturbing the animals we are studying. The coevolution continues and future developments will focus on integrating diverse sensor systems to provide new perspectives for midwater ecology, and on automating research processes to expand the scale of operations, improve efficiency, and promote technology transfer.