Visibility when looking down through a Glass Bottom Boat

[gutman]

TL;DR

Why is there better visibilty when viewing under water through a glass bottom of a boat rather than say looking over the side of the boat?

Why is there better visibilty when viewing under water through a glass bottom of a boat rather than say looking over the side of the boat?

 

[berkeman]

Welcome to PF.

What are your thoughts on this question? Have you been able to find anything with your Google searching so far? How familiar are you with the index of refraction of clear materials?

 

[gutman]

The only reference I could find is on Wikipedia "glass-bottom boat", where it says "The view through the glass bottom is better than simply looking into the water from above, because one does not have to look through optically erratic surface disturbances.". That was my intuition as well, but I'd like to go beyond imtuition... I hope to get some support (or not) for this claim, and more details.

 

[Ibix]

The non-flat surface of the sea means that light paths bend randomly at the surface, distorting images seen through it. You can see this effect in a swimming pool, or even a bowl of water.

Additionally, the sky above you is brighter than the sea below, so you see a lot of light from above washing out what's inside. It's much like looking into a window from outside on a sunny day - you see the exterior world reflected and not much of inside. When you're in a viewing boat the interior will be dim so you don't see so much reflection.

 

[sophiecentaur]

TL;DR Summary: Why is there better visibilty when viewing under water through a glass bottom of a boat rather than say looking over the side of the boat?

Why is there better visibilty when viewing under water through a glass bottom of a boat

Light from the sky (and particularly the Sun, of course) will reflect at the surface of water or glass. For a water surface, with many wavelets, wherever you look on the surface, you can see moving spots of light from which will all 'sparkle' annoyngly. Working under a tent or sunshade wil eliminate most of that. A crinkly water surface will produce specular reflections in many directions (distorting the image due to refraction at the changing surfaces but a plane glass surface will only show one image of the Sun and you can easily move your viewing point to put that image somewhere it doesn't matter.

Glass bottomed boats for tourists usually have a small cabin to reduce significant light interference.