Bring all of the barrels of cream soda to the net, purifying the water, and allowing access to the entire level.
Go to the top cave on the right side of the level and crash into the ceiling, in order to make a worm fall from the ceiling.
Catch the worm and use it to catch Fluffy, the yellow fish wandering around the center of the level.
Go to the second cave from the top on the right side of the level, and use Fluffy to lure the Mullet.
Maneuver the Mullet to the net, although you must be very careful, as the Mullet is very strong, and can easily push the Aqua Grabber 3000 around. After bringing it to the net, drop it in, and you will obtain this stamp, in addition to 1000 coins.
This stamp was released on July 26th, 2010, as one of the original stamps.