you simply cant, you might try to migrate Pokemon from emerald, Sapphire, ect..but you cant because they know hm moves. ive beaten the game and you cant get it, it may look like you can use dive in a certain area but you cant.
In Platinum, Diamond, and Pearl they removed Dive.
You have to delete dive before you transfer it to platinum.
you can't
You, unfortunately, cannot dive on diamond, pearl, or platinum. Sorry.
A dive boat that is restricted in its ability to maneuver.
no
You cannot buy Dive Balls in Pokémon Platinum however you can get Dive Balls from the Newspaper Person in Solaceon Town who asks to see a specific Pokémon every day.
No
u cant srry
Dive is not an HM move in Pokemon Platinum. There are, however, Pokemon that can learn it by level up.
on your way to victory road, in the water you will see a poke ball that is a dive ball
Gyarados cannot learn Dive by itself from leveling and must learn it from the HM Dive which is not available in Pokemon Platinum. The HM for Dive is only available in Pokemon versions; Ruby, Sapphire, Emerald, White, Black, White2, and Black2