Boats can float because of buoyancy.

A boat floats because of which force. The buoyant force pushes upwards against the object. I suppose the ideal boat would be one made of light wood like driftwood. As the ice cube displaces or pushes away some.

Put another way the boat floats because the weight of the volume of water displaced by the boat is greater than the weight of the boat itself. Why traditional and modern rafts float. Objects like boats float even if the metal that makes up their hull is heavier than water because of a force called buoyancy.

Any object placed in water experiences two forces. A boat or any object on the water will float if its downward or gravitational force is less than its upward force or buoyancy. The boat floats in the water because the two forces are balanced weight buoyancy.

If a boat fills up with water the weight of this water adds to the boats weight and there will be less flotation to support the boat. At the same time they are pulled down by the force of their own weight caused by gravity they are pushed up by the buoyant force which is equal to the weight of the volume of water they displace. One of the forces is the gravitational force and the other one is the force of buoyancy.

Gravity is trying to pull your pennies and tin foil downward while the buoyant force is pushing the boat upwards. As the ice cube displaces or pushes away some of the water it causes the level in the glass to rise and your ice cube to float partially in and partially out of the water like a miniature iceberg. A raft is no different.

Buoyancy ˈbɔɪənsi ˈbuːjənsi or upthrust is an upward force exerted by a fluid that opposes the weight of a partially or fully immersed object. To understand buoyant force think about what happens when you put an ice cube into your glass of water. I always thought that boats floated because of their shape.