After you get the Scroll of Obob and wake Bananette, Sub-C is repaired and you continue on your way.

Explore Tunacola

Go east and you will see a fish-shaped island. Dock there, get out at the dock, and go up the stairs. Walk onto the house to enter the village of Tunacola. You have to talk to the boy in the northeast house. You don't have to talk to the other villagers, but you can if you wish. Then leave the village and get back in Sub-C, then go east from the island.

Explore the Big Whale

After a brief cutscene, go west until you see a person next to a raft. Go into the dock and walk up to the person. Talk to him. After he realizes that the lighter is missing, get back in Sub-C.

Find the Lighter

From Baboo, go northeast, then east, then south, then east, then north, then get on the waves in the water and press B to dive.

From where you end up, go north, then west, then west again, then go south but ignore the waves in the water and go west, then get on the waves and press B to dive.

From where you end up, go north, then north again, then west, west again, south, then go south but ignore the waves, go south and then go west through the wall where the bubbles appear in the water. From there, go south, then south until you get out of the submarine, then south, then east, and east again to find the lighter.

Return to Baboo

Go west, then west again, then north, and enter Sub-C. In the big pond, go onto the waves in the northeast part of the pond, and press B to dive. Then you can go south to find Baboo. Talk to him and there will be a cutscene.

Baboo tells you to dip Dr. J's letter in water. Say Yes when Baboo asks if you understand. This is a reference to an actual physical piece of paper that was included with the original NES game. To simulate this, click the bucket or letter below:

📄
frequency
747 MHz
🪣

If somehow the above didn't work: frequency 747 MHz

If you want to see what the original letter looked like, download the StarTropics instruction manual PDF from Archive.org. At the very end of the PDF, there is a picture of the letter with the hidden text revealed.

Return to Sub-C

After the cutscene, you and Baboo and Sub-C end up on an island. When Baboo asks if you understand, say Yes unless you want him to repeat it. Go into Sub-C and Nav-Com will ask you to input the frequency. See above for the correct frequency. Press up and down to select a number, and press A to finalize the current number. If you put in the wrong number, just keep entering numbers until Nav-Com lets you start over.

After you enter the correct number, there will be a cutscene, and you will automatically proceed to Chapter 5: Captain Bell.