When you meet Mrs. Puff in Jellyfish Fields, she tells you that a golden spatula is at the bottom of Jellyfish Lake. You can find Mrs. Puff shortly after exiting Jellyfish Caves. There will be plenty of robots blocking your path, so you need to take them out along the way. To drain the lake, you will need Patrick to complete it. There is a bus station in front of Mrs. Puff you can use to swap characters.
When you have Patrick, proceed to the middle island across the bridge, and there will be three robots with large hammers waiting for you that you need to fight. Take our two of them, and then perform a belly flop next to the last one to stun it. Next, pick up the downed robot and point it at one of the brown pumps sitting in the water. A reticle will show up hovering of the pump, and you can toss the robot to destroy it. You will need to do this until all of the pumps are gone from the water. There are five pumps for you to destroy.
After the final pump is gone, the lake will partially drain, and a golden spatula will be available for you on a small platform. Jump over to it, and then return to Mrs. Puff on the other side of the island to tell her you finished the task. She won’t give you anything for your troubles, but at least you received a golden spatula for your hard work.