Buoyancy is the ability to float on air in water. It is measured by newton's because newton’s are used to measure forces and buoyancy. For a boat to be buoyancy it has to have a smaller weight than the water it displaced. For that reason you need to do it as less dense as possible which will make it weigh less and less dense from water which is 1 N dense. So to make the boat less dense, I tried to the volume of the boat big but leave the mass of it as small as possible, by making it hollow. That way, the density of the boat got smaller than the density of the water and the boat will float. For the stability of the boat, I put two upside down triangles that do the job of two legs. Also, I tried to make my boat as symmetrical as I can so it won't be heavier on one side and tilt that way. You calculate buoyancy you check the weight of that thing, it is equivalent to the buoyancy force.
The buoyancy of the bottle is changed when the density changes which changes when the mass changes
The boat will float since it's weight is smaller than the weight of the water it displaced.
My boat floated with waves but couldn't hold coins because of stability problems.My boat floated since it wasn't denser then 1 N (water density), which made the force of buoyancy work on it. It stayed stable with a bit of waves but the coins broke it since it wasn't stable enough to hold the weight without falling aside.
If I would have another print I would make my boat wider and lower since the boat being high caused it to fall aside when it had a presser of more weight on it. I would make it wider since I still don't want to loose volume which will make it less dense and that way less buoyancy.