65 mangos, 12 coconuts, and three rubber-banded baggies of coffee slide across the deck in two large plastic bins. There’s a broad-built man in a little boat called COUNTRY staring at me. I have no money and it’s 600 miles to the nearest ATM. For four years, I've been traveling the high seas, alone aboard my sailboat BOBBIE. I’ve traveled 15,000 miles of open ocean, through twelve countries on four continents – long enough to know that being cashless doesn’t have to be a problem. For centuries, explorers have ploughed all corners of our watery world, armed with little more than improvised currencies. From the Portuguese pursuits of exotic spices in the Moluccas, to the movement of molasses across the West Indies - the sea has always remained the most flexible of marketplaces.