None. You get the HM move Dive from Steven in Mossdeep City. You have to have the Mossdeep Gym Bagde to use it though.
You don't need a Red Shard for Dive.
to get all the stones you need, first go underwater by using the HMO8 DIVE.. teach it to a water Pokemon then go to the sea behind the the mossdeep city, then go to a part where the water has a color of dark then use dive at the top of it then search for a GREEN SHARD,RED SHARD,YELLOW SHARD or BLUE SHARD.. then exchange that thing to a house behind the mossdeep city then talk to the man inside the house then you have it..
to get a water stone you need to find a blue shard and give it to the man in the house about half way beetween lilycove and mossdeep. (NOTE-to find a blue shard you need HM dive to dive under water.)
You need to get the TM dive.
You will need the Dive HM which I think you get from Stephen after getting the badge from the Mossdeep gym. Then use Dive out at sea and you can find shards underwater aorund the Mossdeep and Sootopolis areas.
There around the hunters house west from mossdeep city. You need the HM dive to find them.
you need to use a water type pokemon and teach it dive or use action replay
well you can get green shards and red shards and blue shard by surfing straight in front of sootopolis city and there will be a dark area dive there catch clamperl and chinchou and relicanth they will be holding shard,s things you need for this: pokeballs hm surf hm dive hope i helped a little
You first need a yellow shard these can be found using Dive near the Hunter's house, Second give the yellow shard to the hunter he will trade you a thunder stone for the shard. Another way to get a thunder stone is by trading a Pokemon from firered or leafgreen that is holding one to ruby, sapphire or emerald.
I have heard there is one on the Abandoned Ship, but I'm not sure. You need to use dive, find a clamperl, use thief or covet on each until you find a blue shard. Then, go to the Collector in Mossdeep and trade the blue shard for a water stone.
I do not have Emerald. But in Sapphire, the Pokemon Relicanth is holding the Green Shard. I caught one and it was holding it. Now I wish I knew what the Green Shard is for! By the way to catch Relicanth you need to HM8 dive. The description I have for the green shard now on my Fire Red is: "A small green shard. It appears to be from some sort of a tool made long ago." yes it is the same for emerald and for the person who answered before me, you can trade it for a leaf stone at the hunters house just to the left of mossdeep when you surf but you don't need to catch one just get a Pokemon and teach it thief or one that learns covet (same ability) which is a zigzagoon at lv28 i think Red - Fire Stone Green - Leaf Stone Blue - Water Stone Yellow - Thunder Stone
get the HM dive and find an area where you can dive there are lots of hidden items and one can be a green shard good luck:) -- The Pokemon Relicanth is holding it. You need to dive into deep water around Sootopolis City and search through the seaweeds. Relicanth is quite rare but I managed to encounter 2 in half an hour. Actually, if you dive around the darker areas near Mossdeep City, you will find small dark circles and they will have hidden items under them.. You can find Green shards under water if you search hard enough, or you can trade it from a friend...