This guide is for Alliance characters who have made it to Menethil Harbor (usually overland from Ironforge), and who wish to reach Gadgetzan in Tanaris.
The first step, regardless of later choices, is to take the ship at the southern dock to Theramore.
From Theramore, the safest way to Gadgetzan, especially for lower level characters, is to swim. You may want to bringswim speed and/or water breathing potions along for the sake of convenience. There are some nasty critters in the Theramore harbor, so as you approach by ship, before you get into the harbor, jump into the water and start following the shoreline south. Pay attention to where you are swimming and stick to the light blue water, as it appears on your mini-map. The light blue water is close to the shore in this area, whereas the dark blue water is further out and will causefatigue.
NB: Swimming from Theramore Isle can be extremely dangerous while in the Dustwallow Marsh waters if you don't take some basic precautions: you're very likely to encounter Young Murk Threshers (level 35) (pleisiosaurs like the ones inDarkshore). Swim around them to avoid their aggro radius. Very rare, but still very dangerous, are Coral Sharks, level 45-46 elites.
There are two swim routes players can take to get to Gadgetzan.
A faster, though nominally costlier way to get to Gadgetzan while swimming, is to strategically die as soon as possible upon entering Tanaris. When you reach the southernmost edge of the Theramore area and you are about to be inThousand Needles, notice that the area changes to Tanaris instead. From now on, all you have to do is drown yourself and rez with the Spirit Healer near Gadgetzan!
Prior to the Cataclysm, players could travel across Dustwallow Marsh into The Barrens. Continuing into The Barrens, taking the first left at the crossroads would bring players to the Great Lift. Once down, after either avoiding or killing the guards, players could travel by foot/mount all the way to the eastern part of Thousand Needles, and then cross into Tanaris. Players may still attempt to jump from the Lift into the water, then swim, but the way through Dustwallow Marsh and to the Southern Barrens is fraught with mobs and the route is significantly longer.