Final Fantasy III/Nepto Temple

Healing Copse
Now that you're out of the nest, it is a good idea to save. Also, equip one of your characters with the Mini spell and walk to the forest to the southwest. Besides a Gnom there are 3 different Springs there. One to revives any deads, one to restore HP/MP and one to cure all status ailments. There, you will receive another Mini spell from a Gnom. Use the Mini spell on all characters. It's probably a good idea to change your physical-based jobs to magic-based jobs, since as Gnomes your physical attacks won't work well. Walk south to enter Tozus.

Tozus
Once in Tozus, walk and enter the house in the northwest corner and talk to the doctor. Give him the antidote and the doctor will open a secret passage as a thank for your help. But before going down check the room for 4 treasure (Mythril Bracers, Fire Staff, Spell Fira and Spell Cura). You may also need to buy some spells for your mages.

Tozus Tunnel
Open the two chests (2x Phoenix Down) and go down the stairs. Walk through the passageway until you are on the world map. Save, then enter Vikings Cove northwest of Tozus Tunnel.

Viking Base
Go east of the bed to the wall, then south through a hidden passages to a chest (Spark Dagger). The door right of the stairs leads to Inn and Shops. Buy Stuff you need and go upstairs. Go west through a secret passage below where a spring that revives any deads and 2 chests (Viking Axe and 3000 Gil).

Go back up and go to Moogle. Near it is a secret passage south to a room with 3 treasures (Fira, Thundara and Blizzara). Continue east, then south and talk with the viking boss. He want you to defeat the sea dragon and in return he will give you his ship "Enterprise". Go north to exit the cave to appear on another part of the world map with a ship nearby. Walk up the coast until you reach a temple.

Nepto Temple
Enter the temple and walk up to the dragon and press. The party will notice a gem missing and the mouth of the statue can be entered. Go inside and walk right until you get to the two holes. Walk into the left hole for two chests (Shell Helm and Shell Armor). Enter the right hole and walk right. Grab the chest (Serpent Sword) and continue right into the hole. Go east until you meet the Giant Rat.

Boss: Giant Rat
If you have a party of mages and high level, then just cast lvl 3 spells on him and you will be done in short time. If not, then continue with lvl 2 spells. After your victory you will receive Nepto Eye. so go back to the temple entrance and press again to put the Nepto Eye back in Statue.

The Nepto Dragon will thank you for your help and reward you with Fang of Water. Go back to Vikings Cove and talk with viking boss again to receive the ship "Enterprise. Now you can go anywhere in the Inner Sea.