As far as I know submarines no longer have optical periscopes but electronic, like a camera if you will.
So no leakage of light.

Still, a whistle sound carry further than your own voice. If a person is too weak to blow a whistle they sertainly won´t get shouting sound of their own. So in any case a whistle is better than no whistle. And since I do not spend any time on water my emergency would appear on land, probably in the forest.I'm going to slightly disagree about the value of a whistle.
This is also correct, there’s a reason you get a whistle on your life jacket. Yet another opportunity to break out your Morse code and start blasting SOS.Still, a whistle sound carry further than your own voice. If a person is too weak to blow a whistle they sertainly won´t get shouting sound of their own. So in any case a whistle is better than no whistle. And since I do not spend any time on water my emergency would appear on land, probably in the forest.
True, Something is better than nothing, so long as one is not too reliant on it. Whilst that experience was on water it applies, maybe even more so, on exposed mountains and areas. In woods though, I should think it would be a pretty good option.Still, a whistle sound carry further than your own voice. If a person is too weak to blow a whistle they sertainly won´t get shouting sound of their own. So in any case a whistle is better than no whistle. And since I do not spend any time on water my emergency would appear on land, probably in the forest.
Had to look it up. I hadn't thought of footy whistles, I think that's a great idea. Tone & "warble" that carries and not likely to be mistaken for wind/gales. I might have one somewhere, the sort with a pea, and it would be much better than my decorative ear-blasting antler tip.My whistle is the Fox 40 classic. There are sound tests on the youtube.
No problem, an ACR Firefly is about £70 (or under 5 cheap strobes) and will provide many years of reliable service, I carried a military version as part of my diving kit for years and years - always worked without fail as long as you look after it. Whilst I agree that knowledge is King, being able to exploit technology is a crucial skill and leaves less to chance. Someone with no tech but all the knowledge in the world is probably not going to be rescued before someone with basic knowledge and an EPIRB.True, Something is better than nothing, so long as one is not too reliant on it. Whilst that experience was on water it applies, maybe even more so, on exposed mountains and areas. In woods though, I should think it would be a pretty good option.
Athos: thanks for good advice, but just seen the prices, sadly out of my price range. This thread kicked off because I saw a cheaper strobe make and thought it might be an option. Non-essential, Something better than nothing, but will probably come with limitations compared to those you have suggested.
IMHO those lifejacket whistles are pretty useless, and forget trying to blow morse while paddling around in the freezing cold sea. On rivers, maybe. Keeping an arm aloft so that they can see you is far more important and effective.
How about a Piccolo, not known as the screaming stick by orchestral players for nothing. When you are rescued you can play the sailors hornpipe on itThis is also correct, there’s a reason you get a whistle on your life jacket. Yet another opportunity to break out your Morse code and start blasting SOS.
Nah, I had one once and to me glotoob is not nearly as bright as the Orbiloc. Orbiloc claims to be seen at 5km.Why not use the glotoob,
from Orbiloc colour guide - "Yellow is often associated with joy, optimism, and energy.""Recommended for an energetic and confident look. Red has a strong emotional association with danger, making it an effective safety colour."This is interesting
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Colours - Orbiloc - The Safety Light
Unique design CHOOSE THE RIGHT COLOUR There are several factors influencing how the different light colours are perceived, such as how the eye perceives different light colours and which specific weather conditions such as fog, rain etc. they are used in. The unique design of the lens and the...orbiloc.com
It may, or may not be helpful

What's so silly about it is it's not rocket science to provide something like a whistle and seal it up so you can instantly know if someone's used it when they shouldn't have.Denying safety rescue kit as staff more concerned with cheating than the life of one of their troop. They could have died of exposure or injury in that 10 hours. Great.