Saltwater/ocean if it makes a difference. On a clear day with no waves. If you were scuba diving, how far down can you be and still see well with only the human eye/no flashlights? (seeing other people, plants, and animals)

Also, if you were at the surface and looked down(with goggles on at the top of the water) how far down could you see?


Visible light is scattered by water. Below 100 meters light rarely penetrates even in clear fresh water. The rule is the more stuff in the water the less light penetrates. In the tropics where sunlight comes nearly straight down on to the water surface it penetrates further in. Water is a very dense material, people forget that because water has no sheer strength, and low viscosity. The difference in properties can be shown by the difference in the speed of sound between air and water. In air the speed of sound is close to 600 feet/second, while in water the speed of sound is around 4950 to 5000 feet/second. The density of water seriously impedes electromagnetic waves, because of this greater density.