Shrimps, mackerels, rays... you'll find them all in the waters where you go out fishing! Type the arrow keys that will appear as soon as you've cast your line. So type the right keys, otherwise your fish will escape! When you've loaded your ship with fish, you go to the harbor to sell your catch. You can use the money to pay toll or to buy a better boat!
Arrow keys = move around.
Space bar = cast line; then use the arrow keys to haul in the line.