In Pokemon Emerald, the move Dive can be learned by a Pokemon of the Water-type, such as Marshtomp, which is the evolved form of Mudkip.

There are a few ways to get Dive in Pokemon Emerald:

1. Move Tutor: You can find a Move Tutor in the Battle Frontier who will teach Dive to any of your compatible Pokemon for a fee of 8 Battle Points.
2. HM: You can also find the HM for Dive in the underwater cave on Route 130 after defeating the Elite Four, which can be taught to a compatible Pokemon, but unlike tutor moves, it takes up a move slot and can’t be forgotten.
3. Level-Up: Marshtomp learns Dive at level 41.
4. Trade: If you have a friend that has a Pokemon that can learn Dive, you can trade with them to get Dive.

Note that you will need the HM06 – Dive, and also need to have a Pokemon that can learn Dive in your party and also have a Pokemon that can use the HM to use it in the field.

How to play pokemon cards

Playing the Pokémon Trading Card Game (TCG) involves two players using their own decks of Pokémon cards to battle against each other. Here are the basic steps to play the game:

1. Shuffle your deck of Pokémon cards and draw seven cards for your starting hand.
2. Decide which player will go first. The first player cannot attack on their first turn.
3. On each turn, draw one card from your deck and play one Basic Pokémon card onto your side of the field if you have any.
4. Attach an Energy card to one of your Pokémon if you have any in your hand. You can only attach one Energy card per turn.
5. Use Trainer cards or Abilities to help you draw more cards, find more Pokémon, heal damage, or disrupt your opponent.
6. Use your Pokémon’s attacks to deal damage to your opponent’s Pokémon. Each attack requires a certain amount of Energy and may have additional effects, such as causing a status condition or discarding Energy from the opponent’s Pokémon.
7. Knock out all of your opponent’s Pokémon to win the game or force your opponent to run out of cards in their deck.

These are the basic rules of the Pokémon TCG, but there are many different cards and strategies to discover as you play. It’s recommended to learn from experienced players or to check out the official rules and guides from The Pokémon Company.