There is a location in the water in World 3-1 where you can go beneath a land mass to access a hidden area, by jumping off of a giant spring arrow. If you curve to the side and go above the normal hidden entrance, you should enter an area where you will be falling towards nothing. Keep going right (stay in the air as long as possible) until you reach the edge. You will be teleported to World 1-1 (and gain credit toward World 3-1) where you can gain more red coins and hearts than the maximum. It will only go to the top, but it will be 10 times easier to perfect the level.