You’re on the beach.
Walk to the upper right along the waterline to reach a cliff. Use the fishing rod to catch a BOTTLE. Look at the bottle in your inventory and use the bottle to take the NOTE out. Look at the note to learn that Indiana Jones needs help.
Walk to the left and try to get the coconut. It’s out of reach so you need some tool to get it. Walk further to the left and read the sign. Use the pile of stones to take one and you’ll meet the Vendor of Stones. Talk to him and when the conversation is over give him what he asked for: the bottle with nothing. You have to be quick though, he’ll walk away right after the conversation.
Use the pile of stones again to take a STONE. Walk to the left twice and look at the sandcastle. Look at the bushes in the lower left corner to find a plank in it. Take the PLANK and walk back to the right to the palm tree. Use the stone on the coconut in the tree. Pick up the COCONUT. Walk to the lower right and see a wild river. Use the plank on the river and step onto the plank. When standing on the plank, take the plank and answer Yes.
The current will take you to the other side of the cliff and to the right of the curtain is some scribbling on the wall. Look at the scribbling and a gameshow will start. The first three answers will be wrong (nevermind) but the last one will be right. You’re a winner!
Your prize is a MATTOCK and you’ll end up on the cliff. You see Rain Island in the distance. Walk to the left and use the mattock on the steps in the rock to climb down to the beach. Walk to the right and pick up the TELESCOPE. Since it’s heavy, you’ll drop the plank. Walk to the left and use the mattock on the steps in the rock again to climb it.
Walk to the right and use the telescope on Rainbow Island to see if you can spot Indiana Jones. Scroll the telescope all the way to the right untill you see Indiana. Leave him and walk back to the left. Use the mattock on the steps again, walk to the right and pick up the PLANK. Look at the wet part of the rocks to find some kind of mineral.
Use the wet stone to pick up the NITRE. Walk to the left and use the plank on the river. Walk all the way to the left, past the sandcastle and look at the altar. There’s a hole in the center. Use the mattock on the coconut to crack it and use the cracked coconut on the hole. A vessel will appear. Look at the vessel and find a tube of GLUE, a corder BAG and a box of MATCHES. Interact with the bag to find sulphur inside.
In the palmtree is a LIANA. Take it. Leave the screen on the upper right to see a big rock blocking the beach. Use the nitre with the bag of sulphur in your inventory and then use the liana with the bag to create a fuse. Use the bag with the coconut to fill the coconut and use the liana with the coconut to tie it shut. Use the fuse on the closed coconut and use the glue on the coconut to make it all stick together.
Put your makeshift bomb on the rock and use the matches on the end of the fuse to light the bomb. You’ve created a passage. Walk to the north to the other side of the rock. Walk to the south and look at the boat. It’s tied to a pole and when you take a closer look at the pole, you’ll see a combination lock. You need to find three digits. Leave the pole and walk back to the south. Enter the bar and talk to the barkeeper.
Ask for a milk and he’ll check the cellar. When he’s gone, talk to the gogo-dancer. Leave the bar and the bartender will return with your MILK. Give the milk to the gogo-dancer and you’ll get a glass with a coin back. Use the glass to get the COIN. Look at the jukebox and use the coin on the slot. Select song #3 and watch the bartender dance.
When he’s on the floor use the professor to search him and find a NOTE. Look at the note in your inventory to learn the code. Take the GLASSES and leave the bar. Walk to the south and look at the pole from the boat again. Use the code as stated on the note and push the green button. Then it’s off to Rain Island.
Game source: A copy of the game was found here on the internet.