The Sundancer has shut it's engines off so it's probably falling almost vertically towards the ground. We're still attached by harpoons to them meaning we're going with them. The cherub used his gravity points to make it so we're now below the sundancer and they're above us, which would pull our boat up due to the harpoons, then Sundancer would continue falling due to no engines and once more pull us down but due to our engines being on, that slows our descent meaning that the Sundancer would fall past us due to no engines, and we'll both be once again in the same position as the start.