*Spoiler* If you haven't gotten that far in Doctor Who. But when I found out that he was The Face of Boe, I kind of figured it out before, but it was still a big surprise. The people of BBC really do know what they are doing.
I am convinced that this was not in the script. Matt was supposed to jump on the hammock and missed, because he’s Matt and he is a danger to himself and others, and this line was just an expression of his confusion.