Have a bit of a thing for free-diving underwater arches.
First one I found was a hole through a fallen slab of rock in a large cave by Navaggio beach on Zakynthos - the famous one with the washed-up ciggy ship rusting on the beach, photographed from the neighbouring clifftop - the cave is clearly visible in most photos. You have to dive fairly deeply on the right-hand-side then ascend through the hole. First time I found it I half-expected to hear a 'pling' and find a rolled-up medikit.

There's another good one around to the right of the monastery peninsula in Paleokastritsa in Corfu, just before you come round into the natural bay you can look down on from the Monastery itself. Again, best to go past it, dive down and rise up as you come back through it. But best to do it accompanied and all at your own risk - though these aren't long tunnels so risk of getting trapped is minimal; so long as you're capable of making the depth.

However, I came a bit unstuck attempting a fairly narrow one near the island rock off Kampos beach (Kefalos) in Kos. It was quite a narrow underwater gully with two arches of rock criss-crossing at one point and flanges of rock either side of the exit. I managed it once on my back, taking a photograph upward. Second time I went through but finding myself short of air, rose a little too early. One ankle and flipper got wedged firmly between the rocks and stopped me short about six inches below the surface. This is not a fun situation to be in.

Desparately fighting the urge to panic and maybe tear my foot off, I pulled myself back down on my own leg, released the flipper, drew my foot out and freed both, before finally surfacing for air.

What I hadn't noticed until then was all the fire-worm stings embedded in my arm and back from faffing about in the tight space, nor the bits of coral that embedded in my back and gave me a nasty cyst just beside my spine.

Though there is worse - apparently there's a deceptive optical illusion in the 'Blue Hole' in the Red Sea, also known as the 'Diver's Graveyard'. It looks like a short underwater hole leading out to the open sea, but is in fact a conical tunnel 26m long that tempts divers down to 52m, and on their 30m dive gear they get nitrogen narcosis and run out of air long before they reach the end, lose bouyancy, and sink all the way to the bottom.
( joefish It's hard for thee to kick against the pricks, Fri 28 Feb 2014, 16:22, 18 replies)

Hehehe
'Flanges'
(bROKEN aRROW PUA HVI Master, Fri 28 Feb 2014, 16:33, closed)

^this

( Smash Monkey lowering the tone of the whole internet, Fri 28 Feb 2014, 16:47, closed)

^ that

( emvee cruor deo cruoris, Fri 28 Feb 2014, 16:57, closed)

Gave me the fear
Have a click!
(SimianKid internet faffer, Fri 28 Feb 2014, 16:49, closed)

Why do you have Mictoboy on ignore, you fucking cunt thistle?

( Richard Shitheels, Fri 28 Feb 2014, 16:57, closed)

:D

( mictoboy shitting in your cunt since, Sun 2 Mar 2014, 11:28, closed)

can someone ask SimianKid why he's got me on ignore?

( mictoboy shitting in your cunt since, Fri 28 Feb 2014, 16:51, closed)

Got me on ignore too.
I'm guessing it's a feeble prick.
( Dr. Shambolic je suis charlie, Fri 28 Feb 2014, 18:13, closed)

Me too. I don't even know who the fuck he is.

( BraynDedd Natasha Kaplinsky's labia majora, Fri 28 Feb 2014, 21:51, closed)

He's not ignoring me, which means I'm more popular than all of you combined.
( Happy Phantom has been to Hastings, Brighton, and Eastbourne too, Fri 28 Feb 2014, 22:38, closed)

In all honesty
I've no idea. I've unignored you now.
(SimianKid internet faffer, Sun 2 Mar 2014, 10:35, closed)

nice one
ta
( mictoboy shitting in your cunt since, Sun 2 Mar 2014, 11:28, closed)

A family friend
A teenage lad got killed like this about 3 years ago, family friend. Very sad
(Smale is stuffed, Sat 1 Mar 2014, 7:19, closed)

Very sorry to hear it.
I've learnt to be very careful trying this, checking both the entry and exit are clear, and to check the underside of the arch before trying to pass through. Anything that looks like 'a bit of a squeeze' is a real no-no, as is any length of tunnel, particularly if there's a cavity underneath as your own bouyancy can catch you out.

I have a colleague who's done some cave diving with full scuba gear, and that's a whole new level of dodgy. Particularly as you have a lot more bits to get trapped, never mind that you're a long way from daylight before you even start.
( joefish It's hard for thee to kick against the pricks, Thu 6 Mar 2014, 16:36, closed)

Was a documentary on that Divers Graveyard a few weeks ago (either Ch4 or 5 I think)
Scary as fuck, there was even some poor guy who'd worn a "helmet cam" and thus ended up videoing his own death.
(localboy purveyor of pisspoor puns, Sat 1 Mar 2014, 8:34, closed)

I watched this too..
If I remember correctly, it was a team of divers investigating some 'curse'

Fascinating stuff.
(danniekavanagh did nothing constructive on, Sat 1 Mar 2014, 12:46, closed)

Urk!!
www.channel5.com/shows/monty-halls-and/episodes/monty-halls-and-the-divers-graveyard
( Jabberwoc misses D.R. and Quinch, Sat 1 Mar 2014, 21:28, closed)

That's the one!
I think what I found more disturbing was when it showed the other deep sea divers picking up all the discarded weights at the bottom of the sea bed..
(danniekavanagh did nothing constructive on, Sat 1 Mar 2014, 21:44, closed)