Based on One Piece Chapters 843, 844, and 845.
This will be a tragedy. You have been warned. Also, Character Death. Again, warnings now.
For two days after that announcement, after their laughing captain suddenly turned serious on them, Luffy refused to budge from that position on deck. His stomach growled loudly but he refused to eat, wouldn't even acknowledge anyone's presence who approached him. He didn't eat, didn't sleep, just stared out at the ocean, as if he was trying to prepare himself for something. By the end of that first day, they realized he was trying to prepare himself in case someone actually did want to leave. He honestly believed that one of them might take him up on his offer, that they might want to leave.
The idiot.
By the evening of the second day, Zoro's irritation had reached the limit. He needed to lash out all his frustration and worry over his captain at someone, so he chose a likely suspect. He lashed out at the man he deemed responsible for all of this, the culprit of Luffy's worry. He snapped and lashed out at Sanji. The battle wasn't like their usual ones, rivals battling to keep each other sharp, competing against each other. This battle quickly took a turn for the serious, until they were both lashing out. Zoro vocally blamed Sanji and while Sanji didn't deny it, indeed, looked suitably guilty over this, he lashed out saying Zoro hadn't done much better than him at alleviating Luffy's fears.
The two continued to battle it out, nearly destroying each other and the Sunny in the process, until finally, someone managed to step in between them.