"Deadliest Catch" captain Sig Hansen, who recently denied his estranged biological daughter's shocking accusations, got emotional when his adopted daughter's boyfriend asked for her hand in marriage.

On Tuesday night's episode of the hit Discovery Channel reality show, fans saw Sig in protective dad mode.

One of his deck hands, Clark Pederson, is also his adopted daughter Mandy's beau. Clark decided to take the plunge and approach Sig for permission to marry her.

Reports surfaced in March that Sig was hit with a lawsuit from his estranged adult biological daughter, Melissa Eckstrom, who claimed her father sexually abused her when she was two years old.

But Sig, long divorced from her mom, has vehemently denied Eckstrom's allegations (made in court documents) as a shakedown for money. Discovery Channel also stood by their beloved reality star.

Sig adopted his second wife’s two daughters, Nina and Mandy, and they have been a happy family for years.

And on Tuesday's "Deadliest Catch," the normally tough captain got choked up thinking about Mandy being ready to get married.

Her boyfriend Clark, who had earlier been ribbed by the crew for making some "green horn" mistakes on Sig's ship The Northwestern, told him in the wheelhouse, "I came up here to talk to you about me and Mandy. Our relationship has been doing really well and it's been progressing. You know we both love each other."

A wary Sig replied, "Yeah?"

"With all the respect I have for her, you, your family, everything going on between us, you've already met my parents…the right thing to do would be ask you for permission to be able to take Mandy's hand in marriage," Clark told him.

The gruff captain asked, "Now--when we're fishing?”

He added, "I know you're sincere, dude, but can we just, like, fish? I gotta absorb this. I know you're thinking about Mandy all the time but right now, let's think about fishing…and then me and you will have a pow wow."

Clark agreed and Sig's crew on the Northwestern proceeded to pull up lots of lucrative crab, the kind that will "buy cars and houses," as their captain boasted.

But once the work was done, Sig looked at pictures of his family and admitted to the cameras that he still saw Mandy as a little girl. Flashback footage showed a loving father-daughter moment on the boat from years before.

"The older she gets, that's really hard," Sig sighed.

"I thought he's just a boyfriend. I didn't know Mandy was serious…I've got a lump in my throat. I don't like it," said the captain, fighting off tears.