Boat
The Boat is given to the Fisherman by the Mayor after he ran his old boat aground in front of the lighthouse in the intro cutscene. The fisherman has to pay back a ship loan of $50 for the boat. Until the debt is paid off, a small a portion of the fisherman's fish sales is taken by the Mayor. A small amount is used to improve the town.
It can be upgraded at the Dry Dock and with every hull upgrade the boat's appearance changes. Other things that change the boat's appearance are the equipment on it. Headlamps are shown on the front, if the boat has lights equipped. A trawl is on the back of the boat, if a net is equipped. Rods will show up as a second fishing rod and a fishing winch. Crab Pots will be visible on the boat's deck. The amount of fish you have will show up as containers on the back of the boat. If the boat takes damage it is shown as fire, smoke, holes on the roof of the cabin, and dents around the boat.
Tips
A quick way to get upgrade materials for the boat is to go to Steel Point, since there is a dredging spot for all three materials there. After dredging out all the materials, simply save and quit. The materials will respawn after loading the game. It is even better to do this after completing the Builder's pursuit as you will have access to your storage on Steel Point.