Tonight, ‘What I found on the Thames today’ is more about ‘What I found out’ than what I found, although what I found out came about because of what I found.

During a recent trip to Putney bridge, a six-pack of diet coke tins floated by, semi-submerged. I was unfortunately too far away to grab them to a) add a photo to our ‘what I found on the thames today’ documentation and b) see if they were empty or full.

This made me think – do cans float when they’re full? Would they float better in a ‘rafted’ six-pack than they would individually? Nick  (a fellow Twilight paddler) promised to go home and experiment. I got off the water and promptly forgot all about it.

Earlier this evening I was pleasantly surprised to hear that he had the answer for me, and it turned out to be an even better answer than I could have expected. It turns out that full diet coke cans do float. More interestingly, however, is that regular (full fat) coke does not*. Bizarre, right? Not really, given the physics of density and the composite nature of regular coke versus diet coke…

“The artificial sweetener used in diet coke is hundreds of times sweeter per unit volume than regular sugar. Classic coke has about 11 teaspoons of sugar in each can, which is taken up by water in the diet coke can. Since sugar is more dense than water, the diet coke will be less dense than classic coke.”

So, next time you’re deciding which soda to take on your kayaking trip, don’t choose diet coke just because it has less calories – consider that it might be useful as an emergency flotation device too, but regular coke is just going to sink like a full fat stone.

*For those sceptics who don’t believe everything written on the internet, rest assured that Nick tested the theory for himself with a can of each, and he confirms that diet coke does indeed float, whereas regular coke sinks.