[Leica] OT: plastic bag for camera

[Xavier Logean <xavier.logean@epfl.ch>]

Hi,

I saw one or twices in magazines that there are some kind
of plastic bags in which you can put your camera.
You can use it for underwater photography.

I am interested to know if this kind
of bags are usefull, practical, ...
when it's snowing, raining, when there is dust and sands, ...
to protect your camera.
Where are they available ? price?

How do they work : is there a plastic or glass  lens on the bag to fix
on the lens of the camera ?

Thanx

Xavier