Flying above an open ocean, Max and the kids are riding in a private jets while being served with snacks and drinks.

"Now this is cool!" Ben cheered. "Picked up in a billionaire's private jet to check out a brand new hotel before anybody else!"

"This could be our best day in summer vacation!" Y/n added. "Thanks, Max."

"I do anything for you guys." Max replied.

"How come you never told us before that you knew Donovan Grandsmith?" Gwen asked in curiosity.

"Must've slipped my mind." Max joked.

The jet reached to the said hotel in the middle of the ocean. The vehicle lowered its wheels and landed on a helipad where two individuals are waiting for Max and the kids. They got off from the jet and greeted the two.

"Max Tennyson, it's been way too long." Donovan greeted.

"How are you, Donovan?" Max shook hand with Donovan.

"Well, with 16 resorts worldwide, I'd say pretty good." He replied. "Glad you finally decide to see how the better half lives."

"These are my grandkids and their friend." Max introduced the kids. "Ben, Gwen, and Y/n."

"And this is my grandson, Edmin." Donovan introduced the kid next to him.

"Hi/Hey/Yo." Gwen, Ben and Y/n greeted in unison.

"Yeah. Whatever." Edwin looked away with his arms crossed, not interest with the trio.

"Ready to take the plunge?" Donovan offered.

They entered to a nearby elevator where it's taking them to a large room below. Once they're out, they met a couple of crews working in the area with a huge round seat like buoy in the middle. They took a seat comfortably, and the crew on a control panel pressed a switch that bringing the group deep into the ocean.

During their travel to the deep below, passing through an underway tunnel, a huge sperm whale passed by.

"Sperm whale." Y/n identified under his breath. "We must be 1000 meters deep or below."

"You sure this is the safest place to build a resort like this?" Max asked Donovan.

"You're talking under water flatline?" Donovan asked back for confirmation.

"I'm talking more like you smacked depth in the middle of Bermuda Triangle." Max clarified.

The Tennysons cousins and Y/n are shocked to hear it, especially the Nemetrix wielder.

"Excuse me? What?!" Y/n exclaimed.

"Growing up, you always were the worrywart, Max. Never the risk taker." Donovan mused. "I give you the world's first and only underwater resort."

Ben and Gwen are in awed as the facility came into view as the hotel is held within a massive dome that protecting it from the crushing depths of ocean.

"You won't believe what's down here." Donovan added.

"Red flag..." Y/n muttered.

They arrived to their destination, and the Tennysons cousins rushed forward with glee with Y/n following behind, passing by a couple of employees. While the cousins went to look at the school of fish, Y/n gazed at large submarine on its station nearby. He whistled in impress manner before he joined the two and noticed a diver doing some window cleaning.

"I read about your resort in 'Pacific Monthly Oceana', Mr. Grandsmith." Gwen said to Donovan. "Very cutting edge. Isn't the glass reinforced with-"

"Butt-kisser." Edwin coughed, interruption Gwen.

"Micro-Titanium threads to withstand up to 10 atmosphere." Donovan elaborated. "Nobody gets wet here unless it in one of the nine pools."

"Very impressive, Donovan." Max complimented.

The Nemetrix wielder remained quiet as he kept looking into the water, not minding the conversation between the Tennysons and the Grandsmiths. Suddenly, the lights began flickering as an alarm blared out.

The previous diver began acting up and noticed that a turbine below is pulling him down. Luckily, his oxygen tube wrapped around his leg, preventing him from getting shredded.

"What happened?!" Y/n asked in panic.

"A power surge must've cause the water to suddenly recycle itself." Donovan assumed.

"Will he be okay?" Ben asked.

"If the sharks don't get him first." Edwin said casually as two sharks began to circling around the diver.

"I can't have an employee turn into a fish food right before the opening. The press will ruin me!"

Donovan rushed away to get help while Ben quietly went somewhere quiet. He transformed into Grey Matter but was aiming for Ripjaws. Y/n decided to stay since most of his aliens are too big to keep a low profile.

Grey Matter dived into the nearest pool and swam his way to the diver. He latched onto one of the shark's dorsal fin, resulting the predator to swim away. The frog alien punched the shark's eye repeatedly until it bite his friend away from the diver.

Grey Matter detached himself from the shark and landed onto the diver's helmet. Then, the turbine began to spin in reverse, pushing the diver outside the pool and launched Grey Matter away.

Once the diver is on the surface, Max quickly pulled him out of the water as Donovan returned to his employee. Luckily for him, the diver is safe.

"Where's your cousin?" Edwin asked Gwen.

"Just hanging!"

They all looked up to see Ben literally hanging onto the tail of a submarine.

"Good one, Ben!" Y/n chuckled.

"Thanks!" Ben replied. "But joke aside, anyone have a ladder?"

After the problem has been solved, Edwin began to guide the trio around the facility per his grandfather's request. During the tour, Edwin showed them a submarine that's called the Undersea Manta Ray.

"You guys want to take it for a ride?" Edwin offered.

"Definitely!" Ben answered.

"Why not?" Y/n shrugged.

The kids entered the submarine with Edwin piloting it. The vehicle dropped into the water and descending down as the Tennysons and Y/n are enjoying the sight of different sea creatures.

"Some of these fishes look totally prehistoric!" Gwen stated in joy.

"Although, I bet these guys are just the tip of the iceberg." Y/n added. "I mean, humanity hasn't fully explore the ocean, yet."

Once they're deep enough, Edwin drove the submarine through the water till they found a deep canyon below. Suddenly, Y/n's hair shivered before a large mechanical squid appeared in front of him.

The squid began to break the glass with its jaw before more of its kind appeared and followed suits.

"Edwin, drive!" Y/n exclaimed.

The boy piloted the submarine away from the squids. Some of them lost their grip on their prey and began their chase. The submarine ascended to an under water mine field. Despite the danger, they abled to make through the danger zone.

Although, the squid problem remains as they kept trying to break through the glass. Ben quickly went to the back and finally transformed into Ripjaws. The fish alien came out from the hatch and began to destroy the squids with his jaws and claws.

After finishing the last of the attackers, the watch started to beep. Ripjaws immediately went back into the hatch and transformed back as Ben.

The submarine continued to flee from their pursuer and managed to returned to the hotel where both Max and Donovan are waiting for them at the station. Although, the alien squids are still attacking the facility till they broke into the glass.

"I knew you shouldn't have taken it! I knew it!" Edwin yelled at Donovan.

"Edwin, quiet!" Donovan demanded. "I'm assure you there's nothing to do with this."

"We can argue later! Right now, those squids are flooding the hotel and we need to get out of here!" Y/n suggested.

They began to run to the elevator with the horde of squid crawling behind their tail. Once they entered, they quickly ascended to a higher level.

"Donovan, what is going on? What did you take?" Max demanded.

"Okay, the underwater volcano didn't work. The resort was doom. I was about to become a punchline in a bad joke." Donovan narrated. "And I found this, other energy sources in a weird craft way down below. It was like nothing I'd ever seen before."

"And now, those aliens want it back." Y/n facepalmed. "Just great."

Once they are out from the elevator, they quickly rushed to the buoy along with other crews. Although, while they're ascending, the squids managed to break the buoy into half, separating the elders and the kids.

While both Max and Donovan ascending to safety, the kids are descending back rapidly. Not caring Edwin as a witness, Y/n transformed into Tentakrul and saved the kids. He floated on the water and lifted up the kids with his tentacle.

"Whoa! Is that you, Y/n?" Edwin surprised.

"That's not Y/n." Ben said in denial.

"Yeah, right. Good alien just showing up to help us while one of us went missing." Edwin deduced. "That goes for you, Ben."

"As much you wanted to know, we can't explain." Gwen said. "But that energy warp, those alien squids after it and we have to get for it first."

Tentakrul growled softly before placing the kids on the dry tunnel that connecting to the surface. He then made some gestures with his tentacles, telling them to escape and leave the core to him.

"You sure about this?" Ben asked, and Tentakrul replied with a nod. "Then we're counting on you."

"What did he says?" Edwin asked.

"He asked us to leave while he handle the core." Gwen explained. "Can you tell where it is?"

Edwin nodded and looked to the giant octopus. "You'll find it at the center of the resort."

Tentakrul nodded and quickly dived into the water while Ben transformed into Stinkfly and took both Gwen and Edwin to the surface.

The giant octopus struggled his way to his destination, fighting through the alien squids he encountered. Once he made it to the core, he began to overload the energy warp by damaging the machine that holding it in order to destroy the entire hotel along with the alien squids in it.

Once he done his deed, he escaped the hotel and transformed back to Y/n as soon as he reached the water surface, reuniting with the rest. Then, the hotel below is engulfed in flame along with the aliens with it.