you`ll need this The Art of Being a Water Terror - Quest - World of Warcraft
quest.
it starts with Dr. Terrible's "Building a Better Flesh Giant" - Item - World of Warcraft , dropped by Apprentice Osterkilgr - NPC - World of Warcraft
do the quest and accept the next one. open the gate by the water and start grinding with your new vehicle. it has around 18k hp and if you train a bit you can kill the mobs before they reach you. and the best part is: the mobs still give exp. have fun!
edit: changed title.