The deck is not one completely from my imagination, I took another persons deck and made it, in my opinion more consistant.
Main strategy: Use Nagenadel to repeatedly add cards to your opponents via Nagenadels GX attack. Vaporeon changes its type to water via it's Aqua Effect Ability (it doesn't loose Dragon though). Then use Misty & Lorelei to use the GX attack again and again. Once your opponent has taken a ton of prizes, use shaymin V/STAR to deal MASSIVE damage.
Your one and only draw engine in this deck is Nagenadel GX, which I think needs to be made more effective in a way. this deck IS very tight however. Regular Naganadel CAN be used, however, it's main perpose is to be discarded to draw 3.
Since you discard a lot of cards with Misty & Lorelei, I added Brocks Grit so that you have some lee-way on discarding important cards early on. Note: Adding items that do the same thing, but the supporter count isn't so high that this would be a problem. Remember, discarding pokemon, energy, and supporters is not a LARGE difficulty to recover, plus you can't realistically deck out with the low draw power + Brocks grit.
The reason that there is so many Proffesors letter is because of the strange 4 different energy types, but more importantly, its an item that gets two cards for one. Often your one card off of using Misty & Lorelei, as you need a minimum of 6 cards in hand BEFORE you play it.
Water engy is so that you can begin to build you hand back up whilst discarding 5. This deck can brick. Beware. But it's also very satisfieing to donk your opponent with 540+ damage for only 2 energy. Shaymin was a good addition to the deck.