Luke: All right, I'll give it a try.
Yoda: No! Try not. Do. Or do not. There is no try.

Luke raises his hand, and slowly, the X-wing begins to rise out of the water - Yoda's eyes widen - but then the ship sinks again.

Mark Hamill: "Um, George..."
George Lucas: "What is it now?"
Mark: "So... according to the script, next I say, 'I can't. It's too big'."
George: "That's right."
Mark: "Shouldn't Luke maybe give it another shot?"
[...]