One Piece Chapter 28, page 15: The Crescent Moon

Usopp explains that he overheard the pirates planning at the shore, so he assumed they would attack from the south. Luffy asks, "HURRY! WHICH WAY ARE THEY GOING TO ATTACK THE VILLAGE FROM?" Usopp replies, "GOING IN THAT DIRECTION IT'LL ONLY TAKE 3 MINUTES! THE LANDSCAPE ON THAT SIDE IS BASICALLY THE SAME AS THIS ONE! ALL WE HAVE TO DO IS PREVENT THEM FROM COMING ON TOP OF THE SLOPE!" Nami suddenly realizes, "OH NO! THAT'S WHERE WE DOCKED OUR SHIPS!! MY TREASURE IS GOING TO BE ROBBED!" Luffy dashes off, shouting, "I ONLY NEED 20 SECONDS TO GET THERE!" Usopp laments, "DAMN! THEN OUR OIL TRAP AND PREPARATIONS ARE USELESS!" As Nami tries to run, she slips on the oil, screaming, "DAMN IT! HELP! I'M SLIPPING!" Zoro yells, "NAMI! WHAT ARE YOU DOING!?"