The Sea Incense is in Lost Cave, which is located north and then east from Five Island. Once you’re inside of Lost Cave, you’ll need to go down the ladder and follow the cave pathways in this order for your Sea Incense: east, north, south, north.
Once you’ve walked through the doors in this order, there will be a Poké Ball in the middle of the room. That Poké Ball has the Sea Incense.
The Sea Incense actually can’t be obtained until late in the game (after defeating the Elite Four).
The prerequisites are basically being able to reach Lost Cave near Five Island. Specifically, the prerequisites here are:
- Have the Rainbow Pass (Help Celio find the Sapphire and obtain the National Pokédex from Oak by beating the Elite Four, and collecting 60+ Pokémon)
- Have a Pokémon that knows Surf
Once you have the Rainbow Pass and can Surf, you’ll be able to get the Sea Incense no problem.
Sea Incense Location Guide
Step 1: Getting To The Lost Cave
If you have the Rainbow Pass, then you can take the Seagallop Ferries from Vermilion City to Five Island.
So visit Vermilion and board the ferry.
Once you arrive at Five Island, head to the northwest side of the island and use Surf.
The Surf path is pretty linear:
Sail north until you reach a wall of rocks, then start heading east until you reach an island with a building on it (Resort Gorgeous).
Then on Resort Gorgeous, go to the east side and use Surf again.
This time there will be two little rocks you will have to sail between, but just keep going east from Resort Gorgeous.
Once you’re through those rocks, just keep heading east and you’ll shortly come across a small island with a little cave on it – this is Lost Cave.
Step 2: Finding the Sea Incense in Lost Cave
Once you’re in Lost Cave, take the ladder down.
There will be a cave entrance on all four walls.
Lost Cave is actually a small puzzle, and you can get certain items inside based on what pattern you take when walking through these entrances.
To find the Sea Incense, walk through the holes in the following order:
After you walk through the final northern doorway, you’ll wind up in a small room with a Poké Ball in the center.
Pick up the Poké Ball to receive your Sea Incense.
Note: Make sure to take good care of your Sea Incense, because you can only get one. And it’s the only way to obtain an Azurill in Pokémon FireRed and LeafGreen!
What Does the Sea Incense Do?
In Pokémon FireRed and LeafGreen, whichever Pokémon holds the Sea Incense will have the power of its Water-type moves boosted by 5%.
This may not seem very good, especially compared to Mystic Water, which will boost the power of Water-type moves by 10%. And truthfully the Sea Incense power boost really isn’t that good.
However, Sea Incense also has another purpose:
Using the Sea Incense while breeding is the only way to obtain an Azurill.
If you place two Marill (one male and one female) into the Daycare on Four Island, they will usually produce a Marill egg. But if one of them is holding the Sea Incense, they will produce an Azurill egg.