Lagoona Trenches

Lagoona Trenches are where underwater mining takes place. Located at the bottom of Lagoona Lake, this place is only accessible from the Underwater Mining Vessel in Lagoona Research Lab. Players can find a vast and varied amount of items hidden deep within undersea rocks. These treasures consist of fossils, Evolutionary Stones, and other rare commodities, such as Heart Scales, Rare Bones and Odd Keystones.

Underwater Mining Vessel
The Underwater Mining Vessel is a small, yellow submarine that the player must operate in order to access the Lagoona Trenches. Talk to the blonde female scientist in the centre of Lagoona Lab and use an UMV Battery in order to activate the UMV and dive underwater. The first time player arrives in Lagoona Lab, the blonde scientist will offer the player a free UMV Battery. When underwater, the right bar indicates the battery status of UMV Submarine. Driving around and mining causes the battery to deplete, and when the bar is empty, the player surfaces and is sent back to the Lagoona Lab. If the player has run out of batteries, he or she will either have to win UMV Batteries from Foxy's Lucky Lotto as a prize, or buy more with Pokédollars from the same blonde scientist in the following packs:

''Note: The player is required to save before mining. This is to prevent players from using the free battery over and over again to get the items they want. ''

NOTE: If the game unfortunately crashes or is suddenly disconnected, the player cannot try again.

Mining
The mining process is nearly identical to Sinnoh Underground in the core series games Pokémon Diamond, Pearl and Platinum, only with hammer switched for dynamites, and the pick changed to a drill. Find and click on sparkling parts of the wall to start mining. Like in real games, if the wall sustains too much damage before treasures are all dug out, it will collapse, destroying all treasures that are not retrieved in time. There is a green bar on the top to show how much damage the wall has sustained, and the player must dig out as many items as possible before the bar fills up.

Each time the player digs, the number of items ranges between 1 to 4 inclusively. The treasures are also similar to those in Sinnoh Underground, meaning that Fossils, Shards, Plates, certain kinds of Evolutionary Stones and some rare items can be excavated, but with the following changes:
 * The 4 fossils found in Unova and Kalos are also added.
 * All kinds of spheres are removed.
 * The Pixie Plate is added.
 * New Fossilized Eggs are added. They yield unique and rare Pokémon, including the Legendary Lake Guardians.

Fossil Pokémon
Certain ancient Pokémon Fossils can be excavated within undersea rocks. Take these Fossils to the back of Lagoona Lab, and talk to the male scientist near the Fossil Revival machine to reap the benefits of player's spoils. They are automatically set to Lv. 10 upon revival. These fossils can also be traded to other Pokémon trainers when given to a Pokémon to hold.

Fossilized Eggs
Different from normal fossils, these Pokémon are hatched from revived Fossilized Eggs found in underwater mining. The Fossilized Eggs are unique to this game. They are stored in the player's party or PC instead of his or her bag. The resurrection process is similar to other fossils — the player must take the Fossilized Eggs to the back of Lagoona Lake Lab and talk to the male scientist for revival. Note that soft resetting does not alter the result. Obtained from Fossilized Eggs, the "Lake Guardians" Uxie, Mespirit and Azelf are the only Legendary Pokémon available in eggs.

Evolutionary Stones
Also found underwater are various Evolutionary Stones that can be used on specific Pokémon to help them evolve. With the exception of Oval Stone, all stones listed below are directly used on Pokémon to trigger evolution.

Other Treasures
There are a handful of other items that can be dug out via underwater mining. The rarity of these spoils varies.

Trivia

 * As surprising as it may seem, Pokémon Eggs can actually be hatched underwater.
 * Some underwater treasures are very rare and have a very high value to other trainers, who might be willing to trade for them in Trade Resort.
 * The music in Lagoona Trenches is based on Through the Sea of Time from the side series game Pokémon Mystery Dungeon: Explorers of Time, Darkness & Sky. This remix theme is made by famous music remix creator GlitchxCity.