How do I go to town for 8 red coins in the wet dry world?

The easiest way is this: do a backward somersault into the painting so you enter it all the way at the top. The water level will now be higher than is usually possible. In the far-right corner of the level, there's a black cage. Just swim over and jump into it. Swim along the tunnel, and you'll find the town.

When you enter Wet Dry World, you're going to haveto make sure the water is at it's highest level. The easiest way to do this is to jump into the painting as high as you can. Once you get the water at it's highest, you will then see in the far corner of the stage, there is a pink bomb omb really high up in the sky, and a cannon. This is near those block with arrows on them, the one's move in the direction the arrow is pointed to when you stand on them. Talk to the pink bomb omb and she will open he cannon for you. Get inside the cannon, and aim to the corner of the world, where you will see a huge cage going down. Shoot yourself in there, and swim along the tunnel (rather quickly so you don't run out of breath!) untill you see what looks like a town. It's easier to lower the water ( the diamond thing to lower it is right below where you entered the town ) here, instead of using the metal mario that you will most likely find at the top.

Hope I helped ^_^