https://techcrunch.com/2021/01/13/these-robo-fish-autonomously-form-schools-and-work-as-search-parties/

Researchers at Harvard’s Wyss Institute for Biologically Inspired Engineering have created a set of fish-shaped underwater robots that can autonomously navigate and find each other, cooperating to perform tasks or just placidly school together.

Just as aerial drones are proving themselves useful in industry after industry, underwater drones could revolutionize ecology, shipping, and other areas where a persistent underwater presence is desirable but difficult.