How deep does a .40 S&W penetrate Water?

At the muzzle, a representative .40 S&W load penetrates approximately 2787 mm (109.7 inches) into water.

What is the impact energy of a .40 S&W?

This .40 S&W load carries about 527 joules (388 ft-lb) at the muzzle.

Penetrates to ~110″ before stopping

Penetration depth

2787 mm (109.7″)

Impact velocity

300 m/s (984 fps)

Muzzle energy

527 J (388 ft-lb)

Bullet behaviour

Intact

Fired at the muzzle, a representative .40 S&W load (11.7 g, FMJ, 300 m/s) reaches roughly 2787 mm (109.7 inches) into water.

Water is a dense fluid medium; bullets destabilise and shed velocity quickly.