Acoustic waves travel more than four times faster through liquid water than they do through open air

A closer look

If you want to be heard faster, start screaming underwater. Sound is just a mechanical pressure wave, meaning it requires particles to bump into each other to propagate. In open air, gas molecules are sparse and lazy, so sound moves at roughly 767 miles per hour. Water, however, is a significantly denser medium where molecules are tightly packed together. When a vibration hits water, those molecules smash into each other instantly, transferring the acoustic energy at a blistering 3,300 miles per hour, making the ocean a terrifyingly efficient echo chamber.