From the start walk down the ramp into the water. Pass by the Rammerhead to reach Green Star #1 then head back towards the ramp. Hook around the pipe to the backside where you can find a Super Mushroom and some clear pipes. Ride the pipe up to the right where Green Star #2 is located.
Take the pipe once more but into the other exit. Make your way to the edge and drop off to the raised level where you can strut to Green Star #3 then into the pipe. At the top you’ll want to fall down onto the P Switch to bring Green Star #4 right to you. All thats left to do is to walk carefully by the Rammerhead along the wooden planks and then up the ramp to Green Star #5 .