Buoyancy is the upward force on an object put in any liquid, in this case, water.
For my boat, I wanted to hollow out as much space as possible, because an object is buoyant if the amount of water displaced is heavier than the weight of the boat. That means that the object would float if the water that would fill the empty space put in the water was heavier than the object.
Although my boat floated in the water, the pennies fell out the back, as the boat tilted, even with the rocking of the water. Improvements that I would make next time would be making sure that the was aligned perfecting in the middle, to make sure it wouldn't tilt to one side.