Captured is the seventh episode of the first season of the animated series.
"Captain Hammerhead captures the Nektons aboard his sub. But his vessel is shonky, rusty and going to sink at any moment. If the Nektons manage to escape, would they help their adversary?"
The Aronaxx receives a distress call from a supposed research vessel only to find a toy submarine, next thing they know the Dark Orca is upon them.
Will and Kaiko attempt to draw the Orca away while Ant and Fontaine return to the Aronaxx to call for help but their pursued and caught by divers, Fontaine does manage to lock the Aronaxx down before the pirates can board it. With their kids captured Will and Kaiko surrender. Once onboard Hammerhead interrogates them believing them to have a valuable treasure, Ant thinking Hammerhead's referring to the scroll nearly blabs to them.
Smiling Finn and Mad Madeline take Ant and Fontaine to the brig while Hammerhead brings Will and Kaiko to the bridge. Unable to break into the Aronaxx Hammerhead decides to tow it back to base and add it to his "mighty fleet", meanwhile Fontaine gets Ant into an air duct just as Finn and Madeline return, Madeline purses Ant who begins messing with the Orca's wiring.
Ant disables the Orca's guidance and sonar before Madeline intervenes, but Madeline accidently trips over a cable that stops the Orca's engines completely, the Aronaxx than hits the Orca's stern causing it to dip down and slowly sink. Hammerhead reluctantly allows Will and Kaiko to go back to the Aronaxx and help save the Orca but makes them take Madeline with them in case the ship goes down (in actuality he wants Madeline to snoop around find the supposed treasure). Fontaine (who escaped Finn earlier) finds a room with diving gear.
Ant overhears the crew and convinces Finn and Madeline to let him use the Shadow Knight to help get the Orca's props moving again. Will and Kaiko return with Madeline to the Aronaxx and attempt to pull the Orca back up but the tow cable strains and begins to give way. Unable to get the prop moving, Ant heads back to the Orca while Finn and three divers move to the Aronaxx to attach grappling irons. Ant convinces Hammerhead to help him with the prop, Hammerhead (through some trial and error) takes the White Knight out to help Ant.
Fontaine is then revealed to be one of the divers with Finn, who allows them to attach the grapples inside the moon pool, they do so just as the tow cable snaps. Meanwhile Madeline searches Will's study area and breaks into the safe containing the scroll. Suddenly the grapples all break and the Orca starts falling, Ant and Hammerhead are able to get the props working again and the Orca surfaces. With the conundrum over Hammerhead orders his crew to take the Aronaxx by any means necessary.
Madeline is caught by Will while trying to steal the scroll. Ant is able to stop Hammerhead briefly and heads to the moon pool, using the claw arm Fontaine grabs Ant who stops Finn and the others inside. Hammerhead quickly returns and battles Ant outside, during the chaos Ant disables the White Knight's life support forcing Hammerhead to surrender. Finn tries to apologize to Fontaine but she doesn't want to hear it.
After returning to the Orca Madeline reveals that she got pictures of the scroll leading Hammerhead to believe that it's full of treasure maps. Back on the Aronaxx Ant notes how well Fontaine worked Finn until that point, the Nektons then receive another distress call.