Click here to view the map of the Sea of Time

If you find a volcano, circle it three times. When the current stops, quickly move ACROSS it.

Now go north and find the first volcano. Go east then go north to the second volcano. Do the same to get across the current. Go north and go west when you see a star. Go to the third volcano. Go south then west to the fourth volcano. Go south and find the fifth volcano. Go west then north to the final volcano. Go north to the next screen.

Here, prepare for a tough battle. You should let Sheba equip the Trident. Go east then north and you will encounter Poseidon.

Battle:: You should exchange all Jupiter Djinn with Piers and give all Mercury Djinn to Sheba. Sheba will then have Wish and Wish Well. Standby 4 Djinn for each each type (except Mercury ones). In the first round, go to item menu and choose Trident. Let Sheba throw the Trident to Poseidon. If you doesn't, he won't take any damage. Revive any dead member if he/she is killed for the first couple of rounds. Basically, try hard to unleash Djinn so that you can summon. Sheba should always use Wish each round. Using this tactics you have no problem to fight this long battle.