Justice League (2001)

S3E1 Monster from the Inferno

Title: Beast from the Depths Plot: The Seaview crew is tasked with uncovering the cause behind a massive communication disruption spanning a thousand miles. Their investigation leads them to a colossal extraterrestrial brain hidden beneath the ocean's surface. Once it is brought onboard, the brain seizes control of Dr. Lindsay, a visiting scientist. With his assistance, and after also taking control of Captain Crane, the alien entity threatens to commandeer the Seaview and subsequently, conquer the Earth.