The Master Plan - S1.E35

During a Terror Fish attack, Stingray is damaged. When Troy goes to make repairs, an Aquaphibian poisons him with some purple liquid. At Marineville, the doctors can't find a cure. Without treatment, troy will die within four hours. Titan has the antidote but will only send it exchange for Marina. Commander Shore refuses but Marina makes up her mind and returns to Titanica. Titan keeps his word and sends the antidote. Once recovered, Troy must come up with a plan to rescue Marina.