The Sea Incense is found on Route 204, which is just north of Jubilife City. But you will need to use Surf to reach the Sea Incense’s exact location.
Sea Incense Location (Step-by-Step)
The Sea Incense is in the southwest corner of a pond on Route 204 – just a short distance to the north of Jubilife City. You will need HM03 Surf to reach this incense, meaning it will remain inaccessible until after you travel to Celestic Town and receive HM03.
But once you have a Pokémon in your party that can use Surf outside of battle, head to Jubilife City and travel north from the Pokémon Center.
Leave town through Jubilife’s northern entrance.
Shortly after setting foot on Route 204, you will pass a pond to your left.
Travel to the end of the white picket fence surrounding the pond and use Surf on the water. You should see a very small opening at the top-left corner of the pond where there’s no picket fence blocking your path.
Surf down and in a patch of terrain at the southwest corner of the pond is a Poké Ball item.
Pick up the Poké Ball to add the Sea Incense to your Bag.
Note: This is the only Sea Incense you can get in Pokémon Platinum.
Sea Incense Details and Uses
Uses in Battle
The Sea Incense is a Held Item that boosts the holder’s Water-type moves by 20%. This makes its effect identical to Mystic Water.
This is a decent item to give a Water-type Pokémon with high Attack and/or Special Attack to further stretch STAB damage. Although other items like the Life Orb and Choice items are more effective.
The Life Orb provides a 30% boost to all of the holder’s moves, not just those of a specific type. The downside is that it takes 10% of the holder’s maximum HP every time they use a damage-dealing move, so a bit more strategy is involved in putting it to work.
The Choice Band boosts the holder’s Attack and the Choice Specs boost their Special Attack, both by 50%; however, these items also force the holder to only use one kind of move until they’re switched out of battle.
The Life Orb and Choice Band/Specs might be stronger, but if you’re not looking to encumber your Pokémon with Hold Item drawbacks (or if you have a Water-type Pokémon who’s lacking an item) then the Sea Incense is not a bad option.
Uses Outside of Battle
You can use the Sea Incense during breeding to get Azurills. Here’s how:
Get two Marills or Azumarills of opposite genders (or get a Marill/Azumarill and a Ditto, or a Pokémon from Marill’s Egg Group).
Then place them in the Solaceon Day Care and give one parent the Sea Incense to hold. If the two Pokémon are compatible to breed, then this can result in the Pokémon producing Eggs containing Azurill, Marill’s pre-evolution form.
Here’s a more step-by-step approach to the process:
Once a Pokémon is holding the Sea Incense, take both Pokémon to the Day Care in Solaceon Town. This building is just northwest of the Pokémon Center.
Give your two Pokémon to the Day-Care Lady at the front desk.
Then leave the Daycare and travel around.
After traveling for a while, return to the Day Care and speak with the Day-Care Man outside. If your Pokémon have made an Egg then he will give it to you.
You can also check your Pokémon’s Egg status on the Day-Care Checker Pokétch App screen, which will display a picture of an Egg if one is produced.
To hatch an Egg, you just have to carry it in your party while you take a certain number of steps.
In this case, it’ll take between 2,570 and 2,826 steps to hatch an Azurill egg.
Note: If you have a Pokémon in your party with the Flame Body or Magma Armor Abilities, that number will be halved.