Fountain of Health
At the start of Chapter 7-1, you'll find yourself back in the Underwhere. Go to the star-marked door at the far right of the screen, past the block-shaped resident. Hit the save block to save your game, then enter the door. Inside is a golden fountain of health. Jump in to fully replenish your HP, and come back any time you need a health boost. Now flip to 3D and go around the first pipe, then take the right path to go over the spikes.
Super Shroom Shake
Take the left path past the second pipe after clearing the spikes to approach a second door. Do not enter it yet. Stay in 3D and approach the switch block ahead. HIt it, then flip the perspective back to 2D. Now you can jump on top of the block and use it to reach the tall pipe to your right. Jump up to collect a Super Shroom Shake, which restores 20 HP. Now enter the door to come upon the Underwhere river.
The Queen
Either pay the ferryman four coins so that he escorts you across the river, or simply swim across the water yourself. On the other side of the purple water, enter the door and climb up the stairs to Queen Jaydes' chambers. Speak to the queen and she will ask you to escort Luvbi to the world called Overthere. Accept her request and a door will appear. Enter it, then hit the star block to finish Chapter 7-1.
Easy Hints
If you get stuck on Chapter 7-1, or any other chapter for that matter, there's an easy way to get free hints on what to do next. First, use a save block to save your game, then take the nearest return pipe to Flipside. Here, go to the fortune teller and pay her fee to receive your hint. Now pause the game and restart your console. You start at your most recent save, and the money paid to the fortune teller will be back in your pocket.