Wang Zhong: "Shells falling on the water can't compare to the damage they do on land. Although underwater shockwaves will injure many people, the water itself absorbs a lot of energy, preventing the waves from traveling far."
Underwater explosions have a smaller lethal range, but their lethality increases. However, the problem is, for the fragile human body, this increased lethality doesn't make much difference.
Whether a person is killed by partial organ bleeding or by all internal organs bursting, there isn't much difference to the dead.
Moreover, underwater explosions also affect the lethal range of shrapnel.
That is to say, there is basically no shrapnel. Firearms designed for underwater use on Earth after the war use special bullets with a lethal range of only about 30 meters.
Don't underestimate "water", this almost incompressible material.