My rationale for my final boat design are that I think my final boat design is great because it has a good shape, it looks well stable to float. Buoyancy is water force which pulls upwards. The role of buoyancy in there is to keep the boat floating with its force. Stability is to stay straight without falling over the sides, or being able to stay still. The role of stability in this is that it helps the boat not to fall on the sides and being able to stay straight.
Volume of Displaced Water Mass of Displaced Water Weight of Displaced Water Buyant Force Weight of Boat
I used those floater to make the boat float because it is a great shape to keep something stable and floatable. Something I should've added is probably some protections on top of the boat all around to keep the coins to not fall. Another thing I could've changed is the surface on top and make it more as a shape so it gets stuck in and it would be harder for the coins to get out.