dont worry about hunter there are no shards in the game! nah just kidding but they're very rare unless your diving. other than that they r super hard to find.
You can find different colored shards when you dive. When you see little dark spots on the bottom of the ocean they're items.
There are an infinite amount of shards that you can get from wild Pokemon and limited ones you can find under the sea in rocks or above in rocks.
Blue Shards can be found on some wild Clamperl.
Red Shards can be found randomly in Dive Spots (the dark patches on the sea, in case you didn't know) on things such as rocks, or crators.
The green shard can be traded for a leaf stone if you talk to the Treasure Hunter on Route 124. Any shards can be traded in for an evolution stone. Yellow Shards = Thunderstones Blue Shards = Water Stones Red Shards = Fire Stones Green Shards = Leaf Stones However there are no shards that allow you to receive a Moon Stone.
Between lilycove and mossdeep cities on the sea
Yellow Shards and the other color shards are used for trading with NPCs for items or moves. For example in Pokemon Ruby, Sapphire and Emerald they are the main source of evolution stones.
you basically look for yellow dots on the map. the yellow dots are iron ores and/or sapphire shards. you have to attack the dome like structure to get it.
all the shards for trading are found in the area west of Mossdeep in dive spots
They are hidden in grass (underwater and above water) and in rocks and walls. Press A, and you should find the shard.
You obtain Leaf Stones by first searching the Pokemon world for green shards. You may then trade those green shards to the Diving Treasure Hunter, who is located at the southeastern end of Route 124 (near Mossdeep City). There are many shards to be found in areas that can be explored with HM Dive.
If you mean Pokemon Ruby, Sapphire or Emeraldm, they can be traded with a hunter on an island halfway between Lilycove City and Mossdeep City. Pokemon Platinum shards are used to tutor moves to Pokemon on Route 212, Snowpoint City, and the Survival Area.