It wasn't so bad at first. The water was clear and light filtered from the surface, but as we went deeper so the light failed rapidly. I had dived often off the coast of England and it is quite light at fifty feet, but diving into a comparatively small hole is different; the sheer sides of the cenote cut off the light which would otherwise have come in at an angle and the general illumination dropped off sharply.
I stopped at fifty feet and swam in a circle, checking to see if the compass was in order. Katherine followed, her flippers kicking lazily and the stream of bubbles from her mask sparkling in the light of the lamps like the fountaining eruption of a firework. She seemed all right, so I kicked off again and went down slowly, looking behind from time to time to see if she followed.
We hit bottom at sixty-five feet, but that was at the top of a slope which dropped into darkness at an angle of about twenty degrees. The bottom consisted of a slimy ooze which stirred as I casually handled it and rose into a smokescreen of sorts. I saw Katherine's light shining through the haze dimly, and thought that this was going to make excavation difficult.
It was cold down there, too. The hot sun merely warmed the surface of the water and, since the warm water was less dense it stayed at the top of the pool. The water at me bottom came from the pores in the limestone all about, and was never exposed to the sun. I was beginning to pet chilled as it sucked the heat from my body.
I signalled to Katherine again, and cautiously we swam down the slope to find that it ended in a solid wall. That was the Absolute bottom of the cenote and I checked it at ninety-five feet. We swam about for a while, exploring the slope. It was smooth and level and nothing broke its surface. The ooze of which it was composed was the accumulated detritus of hundreds of years of leaf droppings from the surface and anything that was to be found would have to be discovered by digging.
At last I signalled that we were going up, and we rose from the bottom of the slope up past the vertical wall of limestone. About thirty feet up from the bottom I discovered a sort of cave, an opening in the sheer wall. That deserved to be explored, but I didn't feel like doing it then. I was cold and wanted to soak some hot sun into my bones.
We had been underwater for half an hour and had been down nearly a hundred feet, and so we bad to decompress on the way up. That meant a five-minute wait at twenty feet, and another five-minute wait at ten feet. When we began diving in earnest we'd have the shot line to hold on to at these decompression stops, but as it was we just circled in the water while I kept an eye on the decompression meter at my wrist.
We surfaced in the welcome sun and swam to the side. I heaved myself out and gave Katherine a hand, then spat out the mouthpiece and took off the mask. As I closed down the valve on the tank, I said, 'What did you think of that?'
Katherine shivered. 'You're right; it's not like the Bahamas. I didn't think I could feel so cold in Quintana Roo.'
I took off the harness and felt the hot sun striking my back. 'It seems bloody silly, but we're going to have to wear thermal suits, otherwise we'll freeze to death. What else struck you about it?'
She pondered. 'The ooze down there is going to be bad. It's dark enough without having to work in the muck we're going to stir up.'
I nodded. 'A suction pump is going to come in useful. The pump itself can be at the surface and we'll pump the mud ashore -- with a filter in the line to catch any small objects. That'll cut down on the fog down there.' Now that I'd seen the situation, ideas were beginning to come thick and fast. 'We can drop our shot line from the raft, and anchor it to the bottom with a big boulder. We're going to have to have two lines to the bottom, because one will have to be hauled up every day.'
She frowned. Why?'
'Come up to the hut and I'll show you.'
We arrived at the hut to find Rudetsky and a couple of his men building a lean-to shelter against one end of it. 'Hi!' he said. 'Have a nice dip?'
'Not bad. I'd like that raft now if you can do it,'
'How big?'
'Say, ten feet square.'
'Nothing to it,' he said promptly. 'Four empty oil drums and some of that lumber we're cutting will make a dandy raft. Will you be using it in the evenings?'
'It's not very likely,' I said.
Then you won't mind if the boys use it as a diving raft. It's nice to have a swim and cool off nights.'
I grinned. 'It's a deal.'
He pointed to the air compressor. 'Will that be all right just there?'
That's fine. Look, can you lead that exhaust pipe away -- as far away from the intake of the air pump as possible. Carbon monoxide and diving don't go together.'
He nodded. 'I'll get another length of hose and lead it round the other side of the hut.'
I joined Katherine in the hut and dug out my tattered copy of the Admiralty diving tables. 'Now I'll tell you why we have to have two lines to the bottom,' I said. I sat down at the table and she joined me, rubbing her hair with a towel. 'We're going down about a hundred feet and we want to spend as much time as possible on the bottom. Right?'
'I suppose so.'
'Say we spend two hours on the bottom -- that means several decompression stops on the way up. Five minutes at fifty feet, ten at forty feet, thirty at thirty feet, forty at twenty feet and fifty at ten feet -- a total of ... er ... one hundred and thirty-five minutes -- two and a quarter hours. It's going to be a bit of a bind just sitting around at these various levels, but it's got to be done. Besides the weighted shot rope from the raft, we'll have to have another with slings fitted at the various levels to sit in, and with air bottles attached, because your harness bottles will never hold enough. And toe whole lot will have to be pulled up every day to replenish the bottles.'
'I've never done this kind of thing before,' she said. 'I've never been so deep nor stayed so long. I hadn't
