Explore Tanaris

Link to map

Gadgetzan (50, 28)
Sandsorrow Watch (38, 27)
Noonshade Ruins (60, 25)
Steamwheedle Port (67, 23)
Zalashji's Den (67, 32)
Lost Rigger Cove (73, 46)
Waterspring Field (60, 36)
Abyssal Sands (45, 41)
Broken Pillar (52, 45)
The Noxious Lair (36, 43)
Dunemaul Compound (40, 57)
Southbreak Shore (64, 60)
The Gaping Chasm (52, 67)
Eastmoon Ruins (47, 65)
Land's End Beach (54, 92)
Southmoon Ruins (40, 72)
Valley of the Watchers (36, 77)
Thistleshrub Valley (29, 64)
Zul'Farrak (38, 16)
Caverns of Time (65, 49)

To make it easier to type into a macro, here's a copy/paste from mklink's reply below. I don't know about the rest of you, but on my screen you can't just copy and paste replies to posts into a macro. It has it in a linear form instead of on separate lines. Here is the same macro in easier macro format:

/way 30.62 64.56 Thistleshrub Valley
/way 34.25 47.71 The Noxious Lair
/way 41.30 56.76 Dunemaul Compound
/way 40.83 72.10 Southmoon Ruins
/way 37.47 78.58 Valley of the Watchers
/way 49.45 84.76 Land's End Beach
/way 53.88 68.19 The Gaping Chasm

/way 47.28 64.75 Eastmoon Ruins
/way 64.09 60.36 Southbreak Shore
/way 72.23 47.07 Lost Rigger Cove
/way 64.56 50.07 Caverns of Time
/way 52.86 45.72 Broken Pillar
/way 44.86 40.16 Abyssal Sands
/way 51.40 29.28 Gadgetzan
/way 39.27 21.47 Sandsorrow Watch

/way 39.38 20.62 Zul'Far

To discover Land's End Beach for this achievement you only need to swim down the coast to about (64,73). That's where you'll discover the zone - then you can turn around a go home.