Why does a boat loaded with too much cargo sink?

A boat loaded with too much cargo sinks because it exceeds its buoyancy capacity. When the weight of the cargo surpasses the boat's ability to displace enough water to stay afloat, it becomes unstable and submerges. Additionally, excessive weight can affect the boat's balance, leading to capsizing. Ultimately, the principles of buoyancy and weight dictate that every vessel has a maximum load it can safely carry.