This will be my guide as to how to quickly(If your lucky) get the sea turtle mount via fishing. i checked around, and i don't think this is a repost, but if it, just close the thread. this'll be my first thread evars, please don't flame meh T.T If you think i left anything out, just tell me, i'll edit it in if its important.
Maybe this time i won't be a complete idoit and post it in the bots and programs section. lol.
I found this spot myself, as well as used it to fish up the mount myself. The islands are much closer together then they appear on the map. With an epic flying mount, it takes maybe 5 seconds to fly between the two, and the islands themselfs are small.
Before you start, you should know:
1. As of current patch, you can still fish up junk, a higher fishing level is advised to save time, as it can not drop on junk loots
2. The mount can ONLY be fished from NR fishing pools, not in open water/frozen sea/rivers/what ever the heck you can come up with.
3. as far as i'm aware, this mount can be fished from pools of blood in BT, when you wash off animal blood in the ocean, though i have not tryed it
4. you could get it on your first cast, or you could cast 1000 times and not see it, its all up to chance
Rods and lures
Rods
Horde have an advantage here, We can get a rod via a quest with +20 fishing very easily, link - item: Nat Pagle's Extreme Angler FC-5000 - Item - World of Warcraft Quest:Snapjaws, Mon! - Quest - World of Warcraft
If you are allaince, i suggest using http://www.wowhead.com/?item=25978, It has +20 fishing, however, isn't quite as easy to get as the horde's rod above. It comes from the quest -http://www.wowhead.com/?quest=10037
If you have already done one of the two quests above, sadly you can'tt redo them and get the rod if you destoryed it/vender. You will have to use a strong fshing pole, which gives +5
ofc, if you have won the STV fishing contest, or have the kaluk fishing pole, these are what you should be using.
Lures
Aquadynamic Fish Attractor - Item - World of Warcraft are what you should be using.
And ofc, if you want to use any of the fishing contest gear, or the +fishing skill enchant to boost your fishing up. Every little bit helps!
Location, and fishing path
You going to want to stay in south DB for this, and follow the arrows and lines on the second screenshot for your path to look for nodes. For the most part, unless you aren't alone, you can always be fishing from a node, with very little(if any) downtime. There is about 5 node spawns on the west island, and 2 - 3 nodes on the east island.
This is the location of the islands.

This is the path you should follow, I would loop around the west island twice before i would fly over to the east island. Forgive my poor arrow drawing skills, the blue dots show where each node can spawn.
Final notes and misc information...
The mount moves at walking speed on land, and +60% in the water. It only requires level 75 riding skill. Here is a link to the mount - Sea Turtle - Item - World of Warcraft
Don't expect it too be a short fishing grind, it took me 2 days worth of fishing, and i know people who it took a week+ to get it. It's come to my attention that, well, its taking people far over 10k, or even 20k casts! It's all about NOT giving up!
I would post screenshots of my mage which has the mount, but my acc is frozen for the time being xD
[Find fish] is your friend.
GOOD LUCK!