Stretsh

Yes, the door needs to be unlocked first. Speedyshel, this is not true. I went from the dragon side and back, and after that I could enter from the volcano. After that, after I died, all I had to do was get 30gp and food, and go the dragon dungeon through Karamja. I mention it here, cause it would be nice if the walkthrough would include this info. It sucks to have to get (buy/make) planks and nails every time you die, while there is an easier way to return.

In the walkthrough it says that you should repair the boat again when you are killed by the dragon. Another way to return to the dungeon: Ttalk to one of the blue dressed sailors in Port Salim, who will bring you to Karamja (island with the banana trees) for 30gp. Once there, move west to the volcano, where you can climb down to the dungeon. Walk wet-north, open the wall and continue walking (running?) north until you see the dragon. Then just climb over to fight him.