The Deep Shell Well is an area in Super Mario Galaxy 2. It is a well and a mission takes place in it.
The mission begins in the Starting Area. The player should drop down the slide and into the water. They should grab the Green Shell for faster transportation and to defeat the Snoodles. While in the small tunnel, they should go left, collect the Comet Medal, and exit the area. They then should continue going through the water, and defeating the Snoodles. When they get to the upward slope they should go up, avoiding the Urchins and Gringills at the top. They then should continue going through the slope until they reach the Launch Star that takes them to the next planet. Here the player should drop down the hole and grab a Green Shell at the bottom. They should swim through the rings to get a boost while avoiding the Boos and walls. At the end, they should swim up the slope and end up in the Oasis Area. They then should grab the Green Shell to the left of the area, and throw it at the treasure chest, freeing Toad who gives you a Power Star.