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, Reply)