During the first break in the narrative, only Rose's granddaughter and the expedition leader seem to be paying much attention to her story. When it cuts back again after the scene of Jack drawing Rose, they're all listening intently.
The salvage-crew member who talks so exuberantly all through the CGI animation of how the Titanic sank is some great Techno Babble:
Lewis Bodine: Okay here we go. She hits the berg on the starboard side, right? She kind of bumps along punching holes like Morse code, dit dit dit, along the side, below the water line. Then the forward compartments start to flood. Now as the water level rises, it spills over the watertight bulkheads, which unfortunately don't go any higher then E Deck. So now as the bow goes down, the stern rises up. Slow at first, then faster and faster until finally she's got her whole ass sticking up in the air - And that's a big ass, we're talking 20-30,000 tons. Okay? And the hull's not designed to deal with that pressure, so what happens? "KRRRRRRKKK!" She splits. Right down to the keel. And the stern falls back level. Then as the bow sinks it pulls the stern vertical and then finally detaches. Now the stern section just kind of bobs there like a cork for a couple of minutes, floods and finally goes under about 2:20 AM, two hours and forty minutes after the collision. The bow section planes away, landing about half a mile away going about 20-30 knots when it hits the ocean floor. "BOOM, PLCCCCCGGG!"... Pretty cool, huh?
Old Rose: Thank you for that fine forensic analysis, Mr. Bodine. Of course, the experience of it was... somewhat different.
Then he looks absolutely mortified when Rose points out that she was there, as he realizes he's been recounting a tragedy she'd seen kill hundreds of people as if it were a brain-dead action movie.
Especially the part where he describes the stern rising out of the water—or, as he puts it, "she's got her whole ass sticking up in the air — And that's a big ass!"
More Hilarious in Hindsight as subsequent studies on the real Titanic commissioned by Cameron, have shown that the stern likely did not rise more than 20 degrees.
The scene where Thomas Andrews informs the ship's captain and officers that the ship is going to sink:
Andrews: From this moment on, no matter what we do, Titanic will flounder.
Ismay:[incredulously] But this ship can't sink!
Andrews: She's made of iron, sir! I assure you, she can.
There are actually still a lot of funny lines during the most intense moments. It sort of accents the sadness when suddenly you giggle and you're right back to crying. This troper's favorite occurs when Jack and Rose are trying to get up the stairs and someone is in front of them praying....
Random Guy: Yea, though I walk through the valley of the shadow of death....
Jack: You wanna walk a little faster through that valley there?
As Rose leaves a cuffed Jack behind to get someone or something to cut him loose, he yells out feebly, "I'll just wait here!"
"Jack—this is where we first met!" Cue WTF expression from Leo. It was ad libbed by Kate Winslet.
The Throw It In moment from Leonardo DeCaprio where he says that it's "time for me to go back below decks and row with the other slaves."
The alternate ending. Instead of Rose just walking out to the edge of the ship and kinda dropping the necklace into the sea, her granddaughter and the crew members see her standing there and run over. Cue her whipping out the necklace in front of them and threatening to drop it. The treasure hunter says something about "I don't know what to say to a woman who was going to jump off the Titanic when it wasn't sinking and jumped back on when it was..." and he begs her just to just let him hold it. After Rose's whole spiel, she lets him, and when she pulls it out of his hand, he grabs onto it until she gives him a look. And then she tosses it over her shoulder with that same little squeak, and Beard Guy yells "LADY! THAT REALLY SUCKED!" before the whole back-on-the-Titanic scene.
Anybody who speaks Swedish will get a good laugh whenever Olaf opens his mouth. Not to mention when Fabrizzio and his Swedish "roommates" are woken up and one of them very theatrically cries: "Oh my God, there's water everywhere!"
When Jack tries to stop Rose from jumping off the Titanic when they first meet.
Rose: Get away from me. You're crazy!
Jack: That's what everybody says but, with all due respect miss, I'm not the one hanging off the back of a ship here.
Molly Brown has several good ones:
(About the dinner trumpet) "Must they insist on annoucing dinner like some damn cavalry charge?"
(To an officer): Hey, Sonny, you gut us all trussed up, now we're all out here cooling all heels. (then after he says he'll find out): I doubt anyone knows what the hell's going on!
(In a deleted scene, while having tea): "Hey buddy, how about some ice?" (cue iceberg scrolling past the window behind her).