The Calico is once again floating about on the waves—or, to be more specific, the Sargasso Sea. Quinn and Brock are examining the local plant life while taking a nice dip in their underwater gear. As Quinn and Brock are pulling up gooshy water plants from the sea, nearby a terrible monster made from seaweed is growing. With no legs, it has six arms, a sort of beard of leafy growths, a mouth filled with stretchy goop, and two squinty eyes. Brock and Quinn notice it and try to swim away.

Pete and Godzooky, meanwhile, are on the ship looking out over the water, but then Godzooky leans too far over the railing and falls in, taking advantage of his mistake by swimming down to help Quinn and Brock with the plants.

And, boy, will they need it. As the two researchers try to make their escape, Quinn gets grabbed by seaweed tentacles. Godzooky sees the trouble and uses his tail as a propeller to speed up, then battles the seaweedy beast, freeing Quinn and nearly getting killed himself. They all break free and quickly make good their escape to the surface.

Underwater, the seaweed monster continues to grow, taking in the plants around it for sustenance. After a short gorging period, it begins the ascent towards the surface, directly at the Calico. Brock spots the behemoth blip on the sonar screen. The monster bursts from the water and wiggles around for a while before grasping onto the ship. Godzooky is scared of it, so Pete comes to cheer him on and Godzooky calls for Godzilla before taking Pete on his back and flying high into the air. As usual, Godzilla bursts from the water with a mighty bellow and continues to grumble and roar over and over again before actually doing anything.

Finally Godzilla engages the seaweed monster with a mighty blast of his flame breath, but still misses despite the gigantic size of his target. Changing strategy, Godzilla picks the seagreen super beast up from the water, but the monsters' super-long tendrils trip the Big G and cause him to fall. The two green titans dance with each other underwater until Godzilla blasts the creature with his amazing laser eyes, causing the waterlogged hooligan to make like a tree and leaf.

Our human heroes decide to take the Calico away from the area (further out to sea) and end up retreating to an island. Pete is making lunch, which apparently includes a big cake, which Godzooky manages to knock into Pete's face.

Quinn runs some tests on the seaweed bits the monster left behind and discovers it is mutated and energized, thus possessing the ability to call matter unto itself. It is eventually determined that the seaweed monster was caused by radioactivity, thus making him a leafy cousin to the Big G. Godzooky finds some seaweed monster leftovers on the boat as well and kicks it around before taking a nap on some hay with a mattress for a pillow.

Unfortunately, the leftover seaweed bits are growing into new and scary monsters!

In the next scene, it's lunch time! Pete the normally blonde-haired kid has a huge salad to feed to Godzooky, too, and when he carries the bowl over to the monster, his hair suddenly turns brown! Godzooky eats the salad, along with the bowl.

Pete goes off on another errand to set the laboratory timer and is attacked by the monster that has formed there from the leftover splattered pieces of the leaf beast. Brock and Carl come to help and, working together, push the monster off the ship. Godzooky alerts everyone that there is another monster in the hold. When they find it, this particular seaweed monster grows bigger right before their eyes. Godzooky engages the monster by posing for a while, and then runs away. The seaweed creature simply jumps off the boat rather than continue with foolish combat. All the plant monsters come together into one gigantic aggregate beast, bigger than the nearby island. Godzooky zooms off and quickly explains the situation to Godzilla.

The monster attacks the island, and then Godzilla hits the scene. The two monsters struggle with each other while our heroes cheer the Big G on. Godzooky comes to help, but Godzilla scares him away with his bad breath. As they continue to fight, Godzilla tears off another chunk from the weed warrior, but somehow that only makes the monster grow faster.

Quinn realizes that the sun dries out the chlorophyll horror and that they need to get the monster onto dry land. Godzooky, taking his cue, leads Godzilla so that the Big G pulls the monster towards the island. The weedy meanie, however, knows what is up and fights back. Despite the plant monster's protests, Godzilla succeeds at pulling it onto the land, and, deprived of its nourishing salt water needs, very quickly the seaweed monster dries out. Godzilla flames the monster with a nasty gout of flame, and roasts it pretty bad. The monster tries to make a break for it, but Godzilla takes chases and zaps it with his laser eyes. That combined with the sun reduces the monster to a pile of ash. Godzilla roars in triumph, yet another beastly victory to notch into his nonexistent belt.

Later, Godzooky goes swimming and is gone for a long time, thus causing little Pete to worry about the triphibian troll. Suddenly some seaweed comes out of the sea—is it the monster resurrected? No, it's only Godzooky wearing a seaweed wig!