In.

The shadow of Tower Bridge.

Cool, killer Bridge. I don't know if you've seen my movie, but ours is way bigger.

I'm with Jason Momo, a tower of a man himself. How am I doing? Rock like a queen.

Oh, like a queen. I like that. Shoulders back.

There you go. Regal. Very Regal.

He's showing me how Aquaman, the character that launched him into superstardom, might Lord over the River Thames. On a brisk December day in London. What a better time. What an amazing idea. For Aquaman to go on the water. The water warrior completely in his element. Of all of the fight scenes you've done in your career and all of the weapons you've had to use, how does a Trident rank?

I love these things. Yeah, it's.

Pretty cool. And Jason wields it like only he can in Aquaman and the Lost Kingdom, the latest installment of the Blockbuster franchise.

True King, Bill Bridges.

Jason, born in Hawaii, got his start acting after landing the leading role on Baywatch Hawaii. You're a menace.

Go away. I suppose, coffee later would be out of the question.

From his role guarding the beach to now protecting the sea, he's also no stranger to embodying royalty. He's a Gilles. He's known for his role in the hit series Game of Thrones, as chieftain, Cal Drogo. He's also a reigning king of Instagram. For years, entertaining his more than 17 million followers, showing off his grueling workouts, his ace ax throwing skills, and some.

Muddy moments.

Now he's back as the reluctant ruler of Atlantis. This time, teaming up with his former nemesis and half brother.

We travel, brother.

High five. Do not call me brother.

Played by Patrick Wilson of The Conjuring and Phantom of the Opera of Fame. Whatever you.

Believe, this man.

This thing, is not.

Your father.

Back.

On land, the three of us meet up for a spot of tea.

There you go, all ready.

Thanks.

Dude.

Well, tea time, cheers everyone.

Pinkies up.

There, everybody. And spilling on all things, Aquaman.

What's the relationship like, Offscreen? Are you guys this close?

Chemistry is a funny thing, right? I think the relationship on screen has to come from two people that want to be there and want to have a good time. And this guy leads with his heart. So when you see the movie and it's just such an expression of him that you feel like you just want to take.

That energy. So what was it like to be on the same side in this movie?

It's great. I think deep down inside, Arthur really wanted to have a mother and he wanted things to be good. And so we come together to do.

Something positive. I think once you understand the cause of what they're both fighting for, you see that it really is just an extension of the first film.

Much of the cast has been quoted as saying they can't imagine Aquaman being anyone else except for you, except for Jason Momo. And I'm curious, having worked alongside him now in two movies, could you imagine anyone else in the role?

No.

What does Jason bring to this role that you.

Think is so neat? Well, I think he had a lot of ideas for this film. He's got writing credit on the film. He knew the story that he wanted to tell.

I'm throwing the sharks. Jason pouring parts of himself into the DC superhero, from being raised by divorced parents to now becoming a father himself, pulling inspiration from his personal life to redefine the character.

Something I'm excited to see in the next Aquaman is your role as a father in the movie. I know you're a dad in real life. So how did you bring the aspect of being a dad to the movie, especially when it feels like Aquaman's family is under threat? I can imagine you as a protective father.

Yeah, I'm extremely strict and very loving in a certain way, but then I'm extremely strict. That's the one thing I wanted to do because you played this character for so long. You're like, I would love to see him this way because he was just as rough, drunk, not afraid of punch, Superman in the face. He's just very hard and lone. And then you got to see him soften up. The thing that I really wanted to do in this movie, too, which I don't really talk about that much, but because I was raised by a single mother, really taking a moment to go like, that's the real superheroes. Because my mom worked three jobs, raised me on her own. I wanted to make that really clear in the film, just going like honoring single parents. I'm a husband and a father, and I wouldn't have it any other way.

And since his childhood days on Hawaii's White Sand beaches, Jason has been a fierce advocate for environmental conservation.

My whole life, I wanted to be a reimbologist, and then I'm not smart enough and that didn't work out.

That's.

Not true. It is a.

Little bit. It is a.

Little bit. It doesn't mean my passion isn't there. It doesn't mean I don't want to go... Anyways, my passion with the environment now, it's cool because I get to use my platform to help all different types of causes.

A superhero on-screen. But in our world of mere mortals, he's a champion for change as a designated advocate for the United Nations environmental program.

Because of our melting of the ice cap, you're going to see the effects of what's going to get expedited. All the storms are going to come up, and how the ocean's going to rise. You're just going to have a little glimpse of like we need to fix quickly. Without being preachy about it, but doing and crafting in the right way.

Yeah. If one kid could walk out and go, Oh, so what happens if the polar ice caps melt? If you can just have a kernel of a cause in there for someone to walk away with something, I think we've succeeded.

Hi, everyone. George Stephanopoulos here. Thanks for checking out the ABC News YouTube channel. If you'd like to get more videos, show highlights, and watch live event coverage, click on the right over here to subscribe to our channel. Don't forget to download the ABC News app for breaking news alerts. Thanks for watching.