Some recommendation for this experiment will be:
1) The use of a bigger water tank, this will help to minimize the errors when the grades are read, because of the small size of the tank the boat touch the corners of the tank and this can change the real grades of inclination. Not only will a bigger tank help with this, but it with help also making the water steadier. With the small tank that was used any movement move the boat side to side making hard the reading of the grade of inclination.
2) The use of an inclinometer to read the grad of inclination, this method will give a accurate inclination grade, not like the pendulum system that was used during the experiment that give a very big uncertain reading of the inclination grade. I understand the use of the magnet to calibrate the pendulum but at the same time the magnet was causing a movement in pendulum giving a wrong or a hard time to read an accurate grade of inclination.
3) A clear dummy or mark on it that math with the teeth in which it was move will help to. Some time when the dummy was move a double or triple check was needed because the uncertainty of in which teeth the dummy was putted.
4) An just for fun the use of different bottoms shapes of boats , to see if the shape of the bottom of the boat affect the equilibrium of a system and if it affect it, how much the shape can affect it.