World 3-2

First things first, hop into that red pipe. It'll take you straight to the underwater section. Keep an eye out for those water funnels that pop up randomly. They can really mess with your swimming, so try to avoid getting caught in them. You'll see some blocks above; hit them to get a Fire Flower – super helpful down here! Then, just swim through and defeat any Cheep Cheeps and urchins you run into.

When you spot the first Star Coin #1, it'll be down below. You'll need to wait for one of those water funnels to disappear before you can safely grab it. Don't rush it!

After that, swim forward to the Checkpoint. You'll see a yellow pipe surrounded by two constant water funnels. This looks a bit intimidating, but just swim straight through them and quickly enter the pipe.

This next area has moving green block platforms. You'll need to maneuver carefully around them as they shift. There are coins to collect and, right in the middle, Star Coin #2. Grab it! Watch out for a blue Cheep Cheep that might be chasing you; a fireball should take care of it. Once you're done, exit through the purple pipe on the right.

Back in the main underwater area, look up! You'll see a P switch hanging from a pipe. Hit it! This will cause a trail of blue coins to appear. Follow this trail to the right. You'll need to use your fireballs to defeat any blue Cheep Cheeps and urchins that get in your way.

The final stretch can be a bit annoying. The openings between the green block walls move up and down, and there are urchins right between them. Plus, those blue Cheep Cheeps will chase you if you didn't take care of them earlier. Seriously, having that Fire Flower is almost a must for this part. Behind the last two big urchins, you'll find Star Coin #3. Snag it!

Once you've got the last Star Coin, go through the pipe to surface. As soon as you emerge, jump up to the upper-left ledge. Give it another hop, and you'll find a hidden 1-Up! Nice! From there, just head right to the flagpole to finish the level.