Crossing the Ditch is Kiwi/Aussie slang for making a trip across the Tasman Sea.
I’m not sure why, exactly, this body of water is referred to as the Ditch, but it is nonetheless, at least in Oceania.
Fun fact: The first two-person team to cross the Ditch via kayak did so in 2007. The 1372km trip took two months.
(Most people prefer to pay for airfare.)