A jet flies by, and inside, Ben is excited that his grandpa invited him and Gwen on the trip. It belonged to a billionaire, Donovan Grand Smith, and the it seems to be headed to an underwater building entrance. They introduce themselves, though Donovan’s grandson, Edwin, doesn’t seem to be happy much. They head inside the elevator, and they enter inside an underwater resort. The view of the marine life is magnificent and something to see, though Grandpa Max is a bit worried, because the resort is built right in the middle of the Bermuda Triangle.

As they enter the main building of the resort, Ben and Gwen are absolutely excited to see the sights. Edwin seems to continue his rude behavior toward his guests. Suddenly, the lights flicker, and the surge causes the fans outside to reverse. The employee outside was in danger, and to make it worse, sharks were coming and circled around him. Ben comes to the rescue, hoping to transform into Ripjaws, though into Grey Matter instead. The Omnitrix’s green light seemed to have attracted Edwin’s attention, but wasn’t to interested in it and continued to speculate the man outside.

Luckily enough, the fans reversed again, and it caused Grey Matter and the man to be pushed out into the indoor pools, though Grey Matter flew into the air. Donavan told them that he had to increase his salary to make sure that he won’t tell anyone about the event. Donavan wanted to talk to Max more, so he tells his grandson to give Max’s grandkids a tour of the place, though the lot of them didn’t see much interest in each other, after Edwin’s demonstration in treating his guests.

As Edwin gives the tour, an indoor “beach” revealed that he was a good swimmer. Ben mocks him. Then they find a giant submarine, which Edwin offered for them to ride in. This troubles Gwen, though Edwin looks back at her, giving a look that would indicate his answer to such a useless question. Meanwhile, Grandpa Max has his own tour of the place. Donovan explains how the power is taken from volcanic vents. What puzzled Max is what was behind a container-looking machine, though Donavan may be hiding something. He tells his employees to turn on a light that can be seen for over 500 feet above sea level, which demonstrates how much energy the plant generates. To finish the tour, Donovan finds that the Under Sea Manta Ray is gone, and knew that Edwin is up to it.

While the kids are inside the Manta ray, they speculate the beauty of underwater sea life, and Gwen is surprised to see fish that looked prehistoric. Their enjoyment ends however, when all of a sudden, mysterious robotic-looking Jellyfish attack the giant underwater machine. What makes it more strange is that Gwen finds that the ground is glowing below them. The robot droids attack, and was able to break the glass dome of the submarine, making their current position to be in danger.

Edwin pilots the Manta Ray into underwater mines, which made the situation worse, though they were able to get through with ease. The drones follow, while Edwin tries to contact for help. Ben gives a signal to Gwen that he’s ready to use the Omnitrix, and Ben heads back to activate it. He transforms into Ripjaws, and he heads out to fight the mysterious droids. Edwin’s distress call was answered by his grandfather, though he doesn’t seem to believe his story, until Grandpa Max tells him that it wasn’t a joke, until many more were headed up the resort.

Ripjaws fights even more robotic drones, and he seems to be getting through them easily. However, the Omnitrix gives its trademark signal, alerting him that he is about to transform back into Ben. He is in danger, especially when the situation gets worse when he has difficulty opening the door to the inside of the submarine. Grandpa Max and Donovan head to the opening where the submarine enters, and were able to get in, though the problems get only worse when one of the alien drones destroy the glass dome of the resort, making the water pour in and flood. Edwin seems to know what Donovan was keeping from what Max wanted to know about, which probably lured the mysterious drones into the resort. Donovan confesses, and he said that he found a strange underwater power source, and he took it for his own use after the resort was in danger after the volcanic vents were unsuccessful. The resort was flooded, and there was no turning back when they started to head back into the surface. Unfortunately, the aliens come in and tear their ride in half, putting the kids back into the flooded resort, and in danger of being flattened.

Fortunately, Ben transforms into Stinkfly, and carries them into safety, though end up inside the flooded resort. Edwin seems to have figured out the secret, as Ben is always gone when a good alien shows up. Meanwhile, Stinkfly’s wings are wet, so they need to find a way to the power core. Gwen finds a nearby vent where they can travel in. Above sea level, the grandfathers try to contact either them and for help, though it seems to have no luck, as the navy would take time to travel to their location, while the lines in the underwater resort make communication between them and the kids impossible. While the kids travel the vents, it falls into the water, though they end up in another area where there are speedboats available.

They travel the floods with speed, getting away from the aliens. Meanwhile, Donovan wonders how Edwin is doing, and he asks Grandpa Max how he treats his kids. Donovan seems to want some advice from Max, as he seems to have a small bond between him and his grandson. Though the kids may be a screw up at times, Max tells Donovan to let them be and give them the opportunity to do their own things, which explains why the kids follow him around to look up to him.

Inside the resort, they find the core, and Edwin tells them that they should reverse the polarity of the connections to make the resort implode. Upgrade comes to be and bonds with a submarine to get out of the area. Successfully, they rid of all of the aliens, but with the resort with it.

They arrive at the surface, and the grandfathers are grateful for their grandchildren’s safety. Edwin tells Donovan that the resort is gone, though he seems to be okay with it. He has another plan, and he said that it is going to be on the moon, and Grandpa Max and his grandkids laugh to his invitation.