Near the end of Plack Beach is the Sea Pipe Statue. It comes to life thanks to Fawlful and
it attacks...
 Sea Pipe Statue: 

"The Sea Pipe Statue....it's alive"
HP:320
While the blooper is resting on its Pipe Statue, it can go into and out of the pipes until
it points one of the pipes toward Bowser where you have to counter it with a punch or else
the Blooper will ram into you.
What you want to do is to use Bowser's Vacuum ability to suck in the Blooper so Mario &
Luigi can fight it.
Inside Bowser, the Blooper has two options. It can bury itself into Bowser's
fleshy...stuff and causes damage to Bowser or it can charge into Mario or Luigi which you
can counter with the hammer.
Make sure the Stone Blooper takes damage so it will eventually will be blasted out of
Bowser's mouth. To do this, counter attack one of the Blooper's attacks and it will get
its head stuck in the statue after being blown out of Bowser. It will take 2 damage.
This is your chance! Punch and punch the Blooper until it gets its head out of the statue.
Repeat the process and you'll win.
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The statue will turn back to normal and water will burst out of the pipes. However, trees
will appear being Bowser...trapping him in the area.
 Informational Resource: 
Mariowiki.com for some information and picture.