How do you catch the three lake Pokemon in Pokemon diamond?

After you defeat Cyrus (Team Galactic's Boss) at Mount Coronet, you can revisit the three lakes of Sinnoh. All you need is plenty of Ultra Balls and a Pokemon that knows Surf. Go to the lake you want, use Surf, and Surf to the center of the lake. Disembark on the island and enter the cavern. The Lake Legendary will be in the center of the room. Note that when you attempt to capture Mesprit, it will run off and move throughout Sinnoh. You can track it using the Map Poketch App. Go to where Mesprit is (try moving between two different areas, like the Valley Windworks and Route 205, continuously until Mesprit comes to you, then try to catch it) and move through the grass or water of the area Mesprit's in. If you encounter it, it will run away the first chance it gets, so use a move like Block or an Ability like Shadow Tag right away to keep it in battle. Then catch it. Sorry this is so long. Good luck.
added they will be lv:50