In Pokemon Platinum version, HM03 Surf is located in Celestic Town and the player will receive it as a reward for beating the Galactic boss Cyrus. Route 210, which is the road to Celestic Town, is blocked by sick Psyducks, and to pass through the road, the player must first obtain the Secret Potion to use on the Psyducks.
The following shows how the player can obtain the HM03 Surf in Pokemon Platinum version.
After leaving Pastoria Gym, the player will chase a Galactic Grunt and battle him near Lake Valor. Cynthia and the player's rival will appear after the battle and will hand over the Secret Potion for the Psyducks and the Old Charm for her grandmother in Celestic Town to the player.
The player will be able to pass through Route 210 with the help of the Secret Potion and arrive at Celestic Town. Once the player arrives, he will meet Cynthia's grandmother who will tell him about a Galactic Grunt who is guarding the entrance to the shrine.
The player must defeat the Galactic Grunt. Cynthia's mother will appear again after the battle and the player should then hand her the Old Charm.
Cyrus will appear once the player enters the shrine. After beating Cyrus, he will disappear and the player will be rewarded with the HM03 Surf.