Yes, that's right. Yesterday my guild leader was kind enough to invite me to a Lurker Fish Fry and walk me through the fishing achievement. I'd heard that it was soloable, and apparently he'd gotten a tip from a nameless buddy on how to do it with Hallow's End Pumpkin Treats. The trick to reaching Lurker without pulling aggro from any other mobs is to walk across the water. Now I've read on El's site that you can do this any number of ways, but they require some sort of levitate *and* slow-fall ability, which not everyone has. But using the pumpkin treats, this can be done by anyone.
First, you have to bring a decent stash with you. The treat bags only contain a few at a time, so it's hard to build up a quantity of them that way. More likely you'll have to complete one of the Hallow's End quests in Hillsbrad (or Tirisfal) to get a stack of fifteen. Once you have enough treats, just head into Serpentshrine (make sure you're in a raid group with at least one other person). Before you go in and aggro anything, start eating treats. Each time you eat one, you get a random costume buff. You're looking for the ghost costume, to get water walking + safefall. The treats are on a one-minute cooldown, so there may be some boring waiting if you don't get the ghost outfit on the first try.
When you get yourself ghost-i-fied, you can head over to the area where Lurker hangs out. It helps if you know this dungeon, but if not you'll be heading in a northwesterly direction from the starting platform. Once you reach Lurker's pool, just start fishing. If you're worried about repair bills you can take your gear off for this. It shouldn't take long to fish him (it?) up and then you'll have your achievement. You'll also be dead... did I mention this was a suicide run? Rofl!
Anyway, if you want a fairly easy way to get this done without worried about class abilities or purchasing obscure potions on the auction, give this a try. You only have until November 1st tho!