It was a scorching Sunday in July. I was cycling, for the first time, a fixed wheel bicycle, which can't coast as the pedals are always in motion.

By the time I reached Houhai I was cooked. My knees were bright red and my shirt was stuck to my back. I threaded my bike through the crowds until I reached the bathing spot on the east side of Qianhai.

There were several swimmers in the water, including a big fellow with a shaved head. I asked an attractive young woman in a bikini if she'd been for a swim. She replied in the affirmative and pointed out her boyfriend with the bald head.

"The water can't be all that deep if he's standing up," I remarked.

"Well, he is 2 meters tall," she replied. Doreen and Jeremy (the charming couple) are German.

"Why don't you take a dip?" Doreen asked.

No sooner said than done, I stripped down to my shorts and asked Doreen to keep an eye on my hired bicycle. If someone nicked it, I would owe the cycle shop 3,000 yuan ($470) to replace it.

I climbed over the railing and was greeted with smiles from the swimmers. I clambered down makeshift stairs. The water was cool and inviting. But I was swimming through weeds, some of them prickly.

Get over it, I thought. It's a free swim in the open air. What more do you want? Filtered water?

Since then, I've returned many times to swim in the lake, much to the horror of Chinese colleagues who insist it's polluted.

One told me: "People come out of bars at Houhai and are sick in the lake or worse."

I invited our new recruit, Ellie, for a dip a few weeks ago. Workmen were erecting a new white stonewall around the lake. Very elegant.

We changed, climbed over the wall and got into the water. It was an easy swim to the island 150 meters away. We swam through weeds. More weeds growing on the lake bed wrapped around our ankles.

I joked with Ellie that I should invest in a mask, snorkel and fins. Then I could trawl the bottom of the lake for treasure.

Imagine how many couples have had arguments while out rowing or pedaling a boat on the lake.

Perhaps angry fiancees removed their engagement rings and threw them into the water?

Ellie considered my idea, cynically. But as they say, where there's muck, there's brass. Perhaps I should also invest in an underwater metal detector?

We swam back to the stairs and got out. There was no sign of my wife or her friend. Our clothes and towels were gone.

I reckoned the ladies went to the jazz bar a few hundred meters away.

We started to walk along the road, attracting amused smiles from passers-by. I should explain that Ellie was wearing a bikini and I had on skimpy Speedos.

When I glanced back I noticed Ellie had attracted a retinue of male admirers.

The jazz bar was closed. We retraced our steps. I reassured Ellie that the penalty for public indecency is probably only a fine. We could plead ignorance.

"Oh god, can you imagine? Three days in China and I get arrested?" Ellie said.

We kept smiling. Why feel embarrassed, when the situation was so funny?

I told Ellie the other two were probably in a taxi heading home, having forgotten all about our clothes and money.

We found them in a beer garden.

The waitress ushered Ellie into the ladies' restroom to change. The girls explained they had got bored. They thought we'd be in the water for ages.

Last time I swam at Qianhai I was approaching the island when something touched my leg.

It felt like another swimmer. But when I looked there was no one there. I guess it must have been a big fish. Maybe I should add a spear gun to my shopping list?