To get to Krokotopia, you must have finished the main storyline up to talking to Sergeant Major Talbot. He will grant you access to Krokotopia when the times comes.
actually, if you are not in krokoshinx yet, you are no where near the end of krok. do all of your queasts that you have and then do what i like to call, and npc check. go around all of the areas that you have acsess to and talk to all of the npcs, fishing for quests, if you checked all of them (and i mean all of them) and still cant find no queasts, you should send a ticket to support. you will no that you are almost in kroko sphinx when you are asked to do the throne room of fire ( a dungeon). once completed, you will be sent to that dog to the oasis and you can head on to that boat and be on your merry way!
