The moment when Hooper visits the Brody household with some wine as a souvenir. Martin, fed up with the whole shark problem, starts filling his pint with the wine despite Hooper's protests that he should let it breathe. Then, he gives Ellen and Hooper the smallest amount imaginable.
To be fair, Hooper did actually hold up two fingers as a way to tell Brody to stop filling his glass. Clearly, neither of them wanted too much, anyway.
And it's the red wine, even though they're having fish.
"My husband tells me you're in sharks."
When Quint sees the shark cage, he doubts its reliability, saying "you go in the cage. Cage goes in the water. Shark's in the water," then smiles and starts singing "farewell and adieu to you fair Spanish ladies! Farewell and adieu, you ladies of Spain!"
At one point, Quint crushes a beer can in his hand, and Hooper responds by doing the same thing with a styrofoam cup.
The vandalization itself, with a spray-painted shark fin and a speech balloon coming from the beach bunny: "Help, shark!"
And the hint that these were particularly well-researched vandals, drawing the fin in correct proportion to the woman.
Might just be a case of the casting not matching the script, but I always found it amusing how everyone treats Hooper like he's a fresh out of college kid. Dude has gray in his beard.
Dreyfuss was 27 when the film was released, which isn't beyond college age depending on what degree is being pursued, especially in the sciences. Most Ph.D students don't finish their degrees until their late-20s, and even that can be prolonged depending on the research. Also, compared to Shaw and Schneider, he was relatively young. It is true, however, that this was a case of casting not matching the script as the script was adjusted for Dreyfuss.
And people can start to go grey in even their late teens.
Brody and his wife are arguing over whether they should let Michael play in the water.
Ellen: Martin, it's his birthday tomorrow!
Brody: I don't want him out on the water!
Ellen: He's not in the water! He's on a boat. I don't think he'll ever go in the water after what happened.
[She flips through a book filled with illustrations of sharks attacking boats and eating people]
Ellen: Michael! Did you hear your father? Out of the water!
Brody: It doesn't make sense that they pay a guy like you to watch sharks.
Hooper: It doesn't make sense for someone who's afraid of water to live on an island.
Brody: It's only an island when you look at it from the water.
Hooper: That makes a lot of sense.
Hooper watching some of the would-be shark-killers: "Ha ha, they're all gonna die."
Also when he describes the guys who are severely overloading their boat:
"You know those eight guys in the fantail launch out there? Well, none of them are gonna make it out of the harbor alive."
The horrifying scene of Charlie barely escaping the shark ends on a fairly amusing note. He probably says the most logical thing anyone could say after experiencing such fright:
Charlie: Can we go home now?
During the scene with the tiger shark, we get this little gem from one of the fisherman:
Fisherman: Well what kind? What kind of shark?
Hooper: Tiger shark!
Fisherman: A what?
For the last line, it's not so much the quote itself but the tone in which he says it.
Also, as the journalist is trying to get the fishermen to pose for a picture, Quint can be seen cruising on by in the Orca snickering whilst tipping his hat slightly. Obviously he can tell that they've got the wrong shark!
Though it mostly depends on which one you get, the skippers are this at some points in the ride, especially when they playfully alter their spiel to poke fun at some of the guests.