This one is a weird one. Probably best to watch the video for an explanation for how this works, but essentially you use the boat as a platform to jump on to a block you usually don't have access to. Jump over to some nearby vines, sprint on the vines over to a block with a cobweb. Shift to the edge of the block where cobwebs no longer slow you down, and then jump over to the other ledge while not hitting your head. Do another cobweb jump and you're out of the map.