Codename: Icky (S01E16)

In the watery depths of cybersite Aquari-yum, the kids and Hacker go in search of a giant cyber-slug, who feeds on pure energy. The kids and Digit travel underwater in two separate vessels, but Hacker has a listening device that taps into their communications system, allowing him to overhear their plans and track every move they make. (Prime Video)