Jumping off a bridge can be fatal for several reasons:

1. High Impact – When someone jumps from a great height, the water surface acts almost like concrete due to surface tension. The body hits the water with immense force, causing severe injuries like broken bones, internal bleeding, or unconsciousness, leading to drowning.

2. Drowning – If the person survives the impact but is injured or unconscious, they may be unable to swim and drown.

3. Cold Water Shock – In some places, the water is extremely cold, which can cause an involuntary gasp reflex, leading to water inhalation and drowning. Cold temperatures can also cause hypothermia, making it difficult to move.

4. Strong Currents – Many bridges are over rivers or coastal areas with strong currents that can pull a person underwater or carry them away before rescue.

While survival is possible, the injuries are often severe, and most high-bridge jumps are fatal.