From Bulbapedia, the community-driven Pokémon encyclopedia.
The Easy-to-Build Water Deck is a predominantly type deck found in the Team Rocket Strategy Guide. The deck is considered easy-to-build as it contains few rare cards, with the aim that a player of any age or skill level could complete it.
If you're having trouble finding the Pokémon you need, use Krabby's Call for Family attack to thin out your deck. Just be careful you don't fill your Bench with too many Krabbys or you won't be able to play any more Basic Pokémon. If that happens, use Mr. Fuji to shuffle one of your Pokémon back into your deck. Mr. Fuji is also good for saving a Pokémon with a lot of cards attached to it from getting Knocked Out. Psyduck's Dizziness and Dark Golduck's Third Eye can also help find cards you're looking for.
If your opponent is playing a Fighting Deck, he or she won't be happy to see Dark Gyarados, which has Resistance to Fighting. Use Magikarp's Rapid Evolution to evolve into Dark Gyarados if you don't have one in hand. Most of your Pokémon have a Weakness to Lightning, so be careful if your opponent is playing a lot of Lighting Pokémon.