After cleaning, boiling, and storing all the usable whale parts, the family decides to plant some crops on the rocky islet where they found the whale carcass, which they christen “Whale Island.” They sail the pinnace along the coast until they reach the farm where they gather crops for transplanting. While exploring the small islet, Fritz discovers a large sea turtle. They tie it to the pinnace and tow it back to camp, using the shell for a water vessel and the meat for dinner.

Back at camp, the Robinsons weave baskets and fashion yokes and harnesses for the animals to expand their farmland and make planting and harvesting more efficient. One day, when Fritz notices a massive snake slithering through the jungle toward their camp, the family retreats to the safety of Rockburg. The snake, a 30-foot boa constrictor, approaches the front door, at which point nearly every member of the family shoots at it. Unhurt, the snake crawls back into the jungle. Fearing the snake’s return, the Robinsons self-isolate inside Rockburg for three days. While taking the animals out to graze, one of the donkeys escapes and runs straight for the swamp. Too late to realize the danger, it stumbles into the snake’s domain where it is crushed and eaten.