In Qeynos Harbor, jump into the channel and swim under the docks. Swim through the small hole in the east wall and follow the tunnel, and you'll surface in the Smuggler's Grotto ( 887, -32, 36 ) /waypoint 887, -32, 36
The Smuggler's Grotto is a well-hidden room under the Qeynos Harbor docks used by unsavory types to smuggle goods in and out of Qeynos out of sight of the guards. The most important resident of the Grotto is Sprockfuddle, an NPC heavily involved in the Qeynos Betrayal series. Also found down here are a broker and two bodyguards. There is also an unopenable door that, judging by its location, leads to the large unenterable circular building on the docks.