Before you go to jellyfish fields, talk to squidward. He will tell you he is all out of jelly. Go to jellyfish fields. On the left edge of one of the mountains(not the top) you will find a jellyfish hive. Finish the level and talk to squidward. He will give you the glasses.
P.S. Do the same thing for Mr. Krabbs, Sandy and Patrick to get upgrades on your spatula, net launcher and your net.
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