Mario & Luigi: Bowser's Inside Story/Pump Works

Basics of the Pump Works
First you should learn that pressing the A and B buttons orderly (A,B,A,B,A,B) will let you swim, and the wall things will float up when the water is there. You can get rid of the water by moving Bowser away from the Sea Pipe Statue with Y.

New Enemy: Bubble Blooper/Dried Blooper

HP: 23

If there is water, they will be bubble shaped and dodge hammer attacks.

If not, they are dry and thin.

Attack: Stabs into the bros. (Dried)

Counter attack: Jump onto it.

Attack: Rolls into the bros.

Counter attack: Hammer it.

Attack: Bounce Counter attack: Hammer.

New Enemy: Protobatter

HP: 36

It grows when hit.

Attack: Hits batter at the bros which should be hammered to bits.

M and L Blocks
When you see 3 different colored pipes, enter the orange and hit the block to make Ms and Ls pop up. Remember the sequence and hit the blocks with the right hero to earn the Attack Piece.(this may occur again later) Head back and navigate to the nubbin in the next room. Hitting it with a hammer causes a panel to disappear so the bros can swim to the next nubbin. This creates a pipe to enter.

Stingler and Chombones
You need the Stingler to open the yellow door nearby. You must find it, note that yellow pellet guards can be removed by nubbins or pink ! Blocks. The Bros need help smashing the big blocks covering the alcoves. Hit the nubbin at the end of the room to release a red sphere. Push this under the Chombone monster and watch it gobble and smash the block.

Escape
Finally, you found Toadsworth. After learning it, use Mini-Mario to save Toadsworth and hit the nubbin to keep going. Later on, use more Chombones to discover an Attack Piece and the next rooms. Use the huge Chombone to find the last Attack Piece, learning Fire Flower. Then you can grab the Stingler and open the door to the Flame Pipe. You must read the next section before returning to Plack Beach.