In platinum you don't get a HM in the Great Marsh. The HM that is there in diamond in pearl, HM05 Defog, has been moved to the Solaceon Ruins
hm 5 is defog and you can get it from the great marsh in pastoria city as soon as you walk in go to the left and talk to the person with green hair and he will give it to you
its a hm and its called strength
You can just reteach it since HM are reusable.
You can find it at the Galactic Warehouse in Veilstone City.
You need an HM to get rid of it. It's HM05 Defog, which you can get from the first guy on your right after you enter Pastoria City's Safari Park (The Great Marsh). Also, I think only Bird Pokemon can learn it.
you can find it in 2 places: in the great marsh just when you begin you'll find a girl talk to her/in the ruines of unknown at the lowest floor
A trainer in Pastoria Great Marsh has it. If you speak with them, they will give it to you.
Defog doesn't exist as a TM, nevertheless it does exist as a HM in Diamond, Pearl and Platinum. Getting the HM depends on the version of your game. In Pokemon Diamond and Pearl, you get the HM from an NPC when you enter the Great Marsh. You will need the Fen Badge from the Pastoria City's Gym in order to use it outside of combat. In Pokemon Platinum, you will find the HM deep inside Solaceon Ruins. You will need the Relic Badge from the Hearthome City's Gym to use it outside of combat.
The HM Whirlpool is not obtainable in Pokemon Platinum, for there is no use for it during gameplay.
talk to a guy to the right of the entrance in the great marsh. he will give it to you
Dig is not a HM in Pokemon Platinum but a TM, it can be found in the ruin maniacs cave.
in a Pokemon center
talk to the person in the entry of great marsh. she will give you hm05 defog
Select the Hm hit use and select Pokemon
In Pokemon Platinum, Flash is a TM.
HM Defog in Pokemon D/P is held by the person directly to your right (with green hair) as you enter the Great Marsh. Make sure you don't already have it and that you are talking to the correct person.
you can get it in pokemon platinum!