As I said in the title, I was at the firemoth, but in the heat of the battle I used an almsivi restoration scroll to telport myself, and when I returned tyo seyda neen so I could come back to firemoth, the boat that take to firemoth wasnt there anymore. Is there any way to retake this quest????Even if its cheat. Please help me!

Swim or fly to the island and pick up where you left off. The boat will still be at the island and your companions will be where you left them. The boat and companions vanish from the game only when you give the shield to Sellus Gravius.

Didnt know it was possible to get there that way!! Thanks!! Last question, where is firemoth located, and how can I get there by swimming/flying? I mean, wich way should I go from seyda neen?

Have a look-see at your world map (not the paper one obviously) and I think its somewhere to the south-south-west of Seyda Neen (don't quote me on that). It should be in that region.

that is slow if you want really fast to firemoth, take a jump spell and a speed spell.
you must buy and make the speed spell very high.
and the jump spell must be mod to.
otherwise you land in the water.
p.s. if go goin down use a slowfall spell of turn god mode on other wise you death if hit the land.