Turtle Soup

Turtle Soup quest is located in Bolarus Tradewinds Market on Kul Tiras Isle.
It's a part of [spell=265870] quest line to obtain [spell=257167].
You can use Enchant Gloves - Kul Tiran Skinning to speed up skin gathering.
To complete the quest gather 5 [item=161426] by skinning [npc=130776].
You can find them north-west of Kennings Lodge in the Fizzsprings Resort.
For TomTom users:
/way Tiragarde Sound 67.65 58.61 Enriched Rockshell (Turtle Soup)

Turtle Soup video: https://www.youtube.com/watch?v=THjXT2R__cw

Table with all [spell=265870] quests:

Id

Quest

Skill

Questgiver

Zone

Video

1

Brinepinch

30-70

[spell=257147] Rank 2

[npc=136061]

Tiragarde Sound

https://youtu.be/d3kU_sP1E9M

2

In Pursuit of Fashion

30-70

[spell=257150] Rank 2

[npc=136061]

Tiragarde Sound

https://youtu.be/YGMLTyR90N8

3

Bone Needle

100

[spell=257153] Rank 2

[npc=136061]

Tiragarde Sound

https://youtu.be/jTDs0oNO0eM

4

Ivory Handled Dagger

Drop item

[spell=257148] Rank 3

[item=161424]

World Drop

https://youtu.be/np_RPaa2sug

5

Turtle Soup

150

[spell=257151] Rank 3

[npc=136061]

Tiragarde Sound

https://youtu.be/THjXT2R__cw

6

Atal'Dazar: An Unbreakable Bone Needle

150

[spell=257154] Rank 3

[npc=136061]

Atal'dazar

https://youtu.be/hBYfshbPnFk

Skill column is an approximate level you need to have to get this quest. It can be a little bit lower, i provide an info at which level i was able to pick up the quest.
Drop item can drop from skinning the related beast in any zone.

Horde quest chain info is here: Zandalari Skinning

Table with some good skinning farm spots under the spoiler.

Spoiler

Coarse Leather

Coordinates

NPC

Note

Video

Zuldazar

49.04 54.45

Gorillas

May be hard

https://youtu.be/vP6S9UM-jrw

Vol'dun

53.58 15.75

Hyenas

Good amount

https://youtu.be/ptIwrvi5P1I

Tiragarde Sound <- second best

58.47 47.27

Seals

Good amount

https://youtu.be/ZBWXyfxJLO8

Drustvar <- the best

66.01 42.29

Quillrats

Fast respawn

https://youtu.be/CEG4rwH21FU

Shimmerscale

Zuldazar <- second best

64.71 18.38

Serpents, eggs

Spawn from eggs

https://youtu.be/VLvWZAmODGI

Vol'dun

39.33 63.01

Saurolisks

Average

https://youtu.be/FP38FNI1Y90

Drustvar

65.42 39.85

Saurolisks

Fast respawn

https://youtu.be/Ms5pY5QAeNk

Tiragarde Sound

44.10 17.89

Saurolisks

Average

https://youtu.be/OBLlqti4L1k

Nazmir <- the best

64.51 66.02

Razorjaw

Huge amounts

https://youtu.be/YdND9jUiqZ0

/way Zuldazar 49.04 54.45 Gorilla Gorge Coarse Leather farm
/way Vol'dun 53.58 15.75 Bouldered Bluffs Coarse Leather farm
/way Tiragarde Sound 58.47 47.27 Umber Shore Coarse Leather farm
/way Drustvar 66.01 42.29 Hawthorne's Plot Coarse Leather farm
/way Zuldazar 64.71 18.38 Rootway Shimmerscale farm
/way Vol'dun 39.33 63.01 Whistlebloom Oasis Shimmerscale farm
/way Drustvar 65.42 39.85 Drustvar Shimmerscale farm
/way Tiragarde Sound 44.10 17.89 Westwind Weald Shimmerscale farm
/way Nazmir 64.51 66.02 The Shattered River Shimmerscale farm

You get the skins when you loot the turtles not when you skin them.

Which is odd considering this is a skinning quest... and you're collecting skins.