Professor Snail controls the island field office on the ginger island. He also does research on fossils and some other things in the museum.
Follow the steps in this guide to unlock professor snail.
Go to the ship dock and buy a ticket to the ginger island. It will take 1000 gold for the ticket.
You will reach the ginger island very soon, go off the ship and look for 10 gold walnuts on the island. Once you find them out, give them to the parrot and he will repair the bridge for you.
Cross over the bridge, you will find a cave on the other side of the bridge. There may be Professor Snail inside that cave and it can be opened by blasting the entrance with the help of a bomb.
Cross the bridge and go back onto the opposite side. Take some clay from the ground and enter a tent near the bridge, you will find Professor Snail inside it.