The trick to this level is lighting all of the unlit torches in the areas you move through, that’s how the Green Stars appear. With that knowledge, collect Fire Flowers and don’t lose them! Snag a Fire Flower right off the start and light the torches here as you move around the corner. Hit three more and hit the POW Block to reveal a hidden Fire Flower before reaching the top platform. Light this torch and defeat the Piranha Creeper to reveal Green Star #1 .
Head through the pipe and you’ll find another Fire Flower available. It’s possible to climb up and go across the top portion of the river but there is no secret exit this time, just a 1-Up Mushroom and a ticket back to the beginning, this portion is 100% optional.
Light the two torches at the start and leap across the floating islands to the spinning one with the flames. Avoid the Parabones and light the torches in the river, trying not to alert the Piranha Creeper. The next spinning platform has multiple Piranha Creepers and you’ll want to knock them back so you can hit all the torches from this location and best avoid the Fire Piranha Plant that is shooting fireballs at you. The next section requires you to leap across two moving islands. The best way to do this is normal jump then long jump, long jump to the far platform.
Light the four remaining torches and defeat the Piranha Creeper to find Green Star #2 . Down the home stretch simply light all three torches for Green Star #3 and bounce off the Piranha Creeper to cap the Goal Pole.