On Pokemon platinum how do you see a Milotic without battling synthia?

To see a Milotic without battling Cynthia in Pokémon Platinum, you will need to go to Route 224. To get there, follow these steps:

1. Start from Celestic Town.

2. Go south to Route 211.

3. Surf south to Route 212.

4. Surf east to Route 213.

5. Follow the path to the Pokémon League.

6. Enter the Pokémon League building and go to the right.

7. Exit through the back door and you will be on Route 224.

Once on Route 224, you can use a Pokémon with the ability Suction Cups or an adhesive orb to surf on the whirlpools. This will take you to the small islands in the northern part of the route, where you may encounter a wild Milotic.