A Secret Boat Ride: The Search For Cresselia/Darkrai

When entering the Harbour you notice that there is a sign set up that reads the following:

Those who have earned the respect of the local Gym Leader, and want to experience more of what Canalave City has to offer - this is the place to be! Take a ride on the wild side and let your heart shine true! Talk with the Ship's Captain to learn more!

As you scrutinise the sign, the Captain walks over and nudges in the shoulder. "Hey there! Fancy a rare Pokémon sighting? Yes indeed, I can guarantee you one, or maybe even two. I can take you across the waters to visit the Full Moon and New Moon Islands where you can meet a real live Cresselia or Darkrai, respectively. You just lemme know when you wanna go, yeah?" he says in a secretive voice.

So, when you feel up to the challenge, you may post a new thread here, to let the captain know you are ready to visit one or both of the islands. You may end up meeting with Cresselia or Darkrai. What you choose to do next is totally up to you. You may choose to battle with the Cresselia or Darkrai, but under no circumstances is this Cresselia or Darkrai able to be caught.

You must have beaten Byron in the Canalave City Mine Gym before you attempt this challenge. Depending on how you handle this situation, Cresselia may choose to allow one of your Pokémon to learn Psycho Cut. There is also the possibility of receiving a Zap Plate from it. Also, depending on how you handle this situation, Darkrai may choose to allow one of your Pokémon to learn Dark Pulse. There is also the possibility of receiving a Dread Plate from it. If you wish to take on either or both challenges, say so in the post you make when entering the Harbour.