When we sat down at De Visserij Piscadera for dinner we noticed these small plastic bags seemingly filled with water hanging from the ceiling all over. The ordering of food itself was interesting. We stood in a long queue for 40 minutes and when our turn came, Sharmila pointed out the fish she wanted from the display. They took the raw fish and sent in for cooking. I paid and then we sat down at a table by the waterfront. It was then that my attention went to those bags.

What would they be for? My first guess was to keep the birds away. What I could not figure out is why would the birds be afraid of bags filled with water? Eventually, my curiosity got the better of me. I flagged down the gentleman who was seating everybody at their tables and asked him what was going on with the bags.

“It is to keep the flies away,” he explained!
“Flies? How?”
“Well, the inflated bag acts as a mirror. When the fly sees a bigger fly, it gets scared.”
“Ah! Clever!!”

He went away. The couple sitting next to us excitedly said – “We have been discussing this for some time. We were thinking they were for birds. Thank you for asking.”

We chatted for some time – thoroughly convinced about how convex mirrors work and how ingenuous the idea was.

Our friends from the next table left after some time. Sharmila’s food came. I started sipping my wine.

And then it struck me!

“Wait! That makes no sense. If the fly can see a bigger fly in the bag, I should be able to see my image too. That does not happen. It is not a mirror. It is a lens. A convex lens. You can see what is on the other side magnified. You will never see yourself.”

Sharmila level of interest was inversely proportional to the quality of the red snapper she was enjoying. She added some more spicy sauce to her fish desultorily.

I was getting more and more excited realizing the flaw in my reasoning before. She did her usual throwing of cold water on my excitement…

“Stop using logic for everything”.

Somewhat dimmed in my enthusiasm, I decided to quietly Google this.

Guess what? This is a fairly common practice in lots of places – including India. Sometimes they put a coin in the bag.

However, experts are unequivocal in their opinion – this has nothing to do with keeping away flies. There are some plausible theories around refraction one can stand up but all evidence points to no effect whatsoever.

I thought of letting the gentleman know about this on my way out.

Then thought the better of it. If not anything else, it is a great conversation starter for customers!!