You go to Celestic town and once you enter the middle part of the town, and elder will say a spaceman is threatening to blow up to town with a bomb. You go up to him and he will challenge you to a battle. When you defeat him the elder will get the package that Cynthia gave you. Then she will tell you to examine the painting inside. Once you enter the cave and press "A" on the painting, she will come in and say stuff about ancient legend and stuff. Then Cyrus (dude with blue hair) comes in and says a bunch of stuff then challenges you to a battle. If you say yes his Pokemon are:
Sneasel: Level 34
Golbat: Level 34 also
Murkrow: Level 36
Once you defeat him he will make a dark flash and disappear (which is pretty cool). Then the elder with blab and blab about stuff, then she says that her granddaughter doesn't use this item anymore and you can have it. It is (you guessed it) HM 03 surf. Hope I helped.
Sneasel: Level 34
Golbat: Level 34 also
Murkrow: Level 36
Once you defeat him he will make a dark flash and disappear (which is pretty cool). Then the elder with blab and blab about stuff, then she says that her granddaughter doesn't use this item anymore and you can have it. It is (you guessed it) HM 03 surf. Hope I helped.