So, there are 18 of us sitting in a small cavern three-foot deep with orange mud the consistency of clotted cream.
We'd arrived there by ziplining into the mouth of Dark Cave then clambering over rocks and gravel before slipping and squeezing for ten minutes through pitch black narrow, muddy, labyrinthine tunnels and passages before sliding down into the pool.
In only our swimming costume, hard hat and head torch.
Health and safety be buggered. While I didn't let my normal claustro-drowning nightmares get the better of me on this occasion, in bed that night I did contemplate the full potential horror of being stuck in a subterranean labyrinth, fighting blindly for the exit over the drowned or hysterical bodies of my fellow muddy funsters.
Phong Nha was wet. Very wet, very damp.
We'd hoped to escape a wet Hoi An, heading for the Easy Tiger hostel, where we booked straight onto a trip to see the Paradise Cave and Dark Cave, but it was damp all the time we were there.
Still, it all added to the atmosphere...
After spending Christmas Eve at the Easy Tiger roast dinner do and having drunk two bottles of red wine, I spent all of Christmas Day in bed, while Kim went on a bike ride on her own to a local farmstay and chatted with some friendly locals.
Paradise Cave was a much nicer prospect than Dark Cave.
It was very big (longest or biggest in the world, I can't remember), but we walked 1.4 km into it and it was pretty impressive.
Stalactites down, stalagmites up, it was like a Ray Bradbury alien world, some of the formations very Geiger-esque, shadows and cool stillness adding to the mysterious ambience.
Apart from the Chinese family group with video camera, tripod, selfie-sticks and whooping little sh**s in tow, obviously. Where's Alien when you actually need her!?
No cameras in Dark Cave. Here are some shots of the ziplining area, our guide and a temple instead...
Next day we headed by boat for (the eponymous) Phong Nha and Tien Son caves, with two tiny Vietnamese ladies paddling eight big Westerners and a large boat for hours on end. They make them tough here.
Phong Nha Cave was made of three 'chambers' through which we were rowed. This was a safe haven for people during the war. Ammunition and bombs were kept 'safe' at the back, families lived in the centre cavern and the first cavern was muster point, loading bay, entrance, etc.
In eleven years of pretty regular bombing, the Americans only got one bomb through the front door, only damaging it a little. So much for Top Gun.
The final cave, Tien Son - smaller and less impressive than the others - was reached via 300-odd lovely, steep steps, but afforded great views of the surrounding countryside and river.
After another nice feed at our favourite restaurant, the Bamboo, we finally left Phong Nha on the night bus for Hanoi. It was still raining.
