Historically, can you really see under water with your periscope?

[PsFr]

Originally Posted by Paul Riley

Surprised me that,I would have thought a PS in real life would have had no problem viewing under water,as long as the visibility of the water itself was good of course.
I imagine the water in some of the Pacific areas to be almost crystal clear,or at the very least clear.
:hmm:
I myself use the OS to monitor DCs dropping if they are near me,so long as I dont keep it raised too much out of its housing.A useful aid sometimes that tactic.

Wouldn't it be dangerous in real life probably (if you are too deep and do that ) though ? i thought maybe it could damage your periscope with the pressure , not sure if it was built to be deployed when the sub is under periscope depth , well just asking , if someone has a definite answer about this , would be nice to tell , cheers