From the pier at Kewalo Boat Harbor, just ashore of a weathered teak junk, the argument is muted by the wind. But clearly the two men on the deck of the Intrepid Dragon II are having words.

The younger one, wearing a bulletproof vest over a dress shirt, leans close to the older man in a straw hat, black aloha shirt and pants with cuffs rolled up for a flood. It’s an aggressive posture. He takes the old man’s beer, a Primo, and empties it for emphasis.

The old man frowns, although just for a moment. It’s as if they’ve done this before.

But all around them, on a location set of “Hawaii Five-0,” cameras rolling, people are grinning. Theirs is a front-row view of the Caan family dynamic: Father and son, James and Scott, face to face on “Five-0.”

On the episode, which will air Monday at 9 p.m. on CBS (KGMB), James Caan plays retired NYPD detective Tony Archer, a bomb expert who has moved to Oahu to work as a private investigator.

“They came to me and asked me to do it,” the elder Caan said during a break. “Obviously, it would be fun with my son.”

The character was his idea, he said. The only thing he insisted on was that he not be cast as the father of Scott’s character, Detective Danny “Danno” Williams.

“The idea was to be this half off-the-wall retired cop,” he said. “Originally, he was some kind of psychic. He is some kind of homicide genius who is retired, who is an old-fashioned kind of guy, doesn’t go for this computerized stuff.”

And the character has one more important trait: He doesn’t get along with Steve McGarrett, played by Alex O’Loughlin, or with Danno.

“Especially my son,” Caan said.

In real life, though, Caan thinks the world of his 35-year-old progeny, the second oldest of his five children.

“I am very proud of him,” said Caan, who will turn 72 next month. “He’s directed a few pictures. He’s done quite a few already. And he’s a wonderful playwright as well, and a good director.”

Critics could easily label the father-and-son episode a ratings gimmick, but James Caan brings a hefty acting résumé to “Five-0” that includes more than 100 roles in film and television and an Oscar nomination for his supporting role as Sonny Corleone in Francis Ford Coppola’s “The Godfather.”

In 2009 he appeared in “Mercy,” a film written by Scott Caan.

On set, father and son have chemistry “to spare,” said “Five-0” executive producer Peter Lenkov.

“James is a great actor, has amazing presence and a great sense of humor,” he said.

“There’s a real chemistry, an ease to things, not just because they are family, but because they are both talented pros.”

Add O’Loughlin and the bromance he regularly shares with the younger Caan turns into a wild threesome, Lenkov said.

“The banter is hilarious but very natural,” he said. “It’s like these three have known each other for years.”

“Five-0” had been interested for some time in casting the elder Caan in a guest role, but it didn’t come together until last fall when Lenkov and co-executive producer Paul Zby­szew­ski met with the actor. They started talking over breakfast and kept talking through to lunch, Lenkov said.

“And he really knew the show,” Lenkov said. “He’s watching the show regularly. He is watching it probably for his son.”

James Caan said he likes the way McGarrett and Danno are evolving as characters. “The best of the show for me is when they get into these little arguments.”

He said he doesn’t offer unsolicited acting advice to his son, who earned a Golden Globe nomination during his first season of “Five-0.”

“I don’t really like to talk about it,” he said. “Point is, you can either hit the ball or you can’t. We talk about ideas, creative ideas. I’m proud of the fact — I’m honored — that he asks me certain things. It’s a compliment to me.”

Working in television, though, isn’t as attractive to the elder Caan as working on a movie. TV just moves too fast, he said.

“It’s a grind,” he said. “Not as tough as digging ditches or carrying meat, but you have to stay mentally tough and mentally alert and find ways to have fun.”

For that reason, he had mixed emotions about Scott taking the “Five-0” role.

“I know my son’s desires, and I tried to teach him what’s really important in life is that you love what you do, and to keep your integrity.”

As if on cue — well, it was time to get back to the business of acting — the younger Caan strode by his father, tossing him a quick glance.

“That’s my son,” James Caan said, smiling. “He’s a good kid.”