Surf is HM #3. :-)
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Get the HM Surf then teach it to a pokemon.
beat the fifth gem leader than you get the Hm surf
HM03
The HM Whirlpool is not obtainable in Pokemon Platinum, for there is no use for it during gameplay.
The elder in Celestic Town. It's part of the plot (You need surf to get farther in the game, significantly), so it shouldn't be too hard.