Tuesday, September 22, 2009

Swimming and physics

"So how's your swimming going?" asks a friend of mine over beers last night.

While I was on holiday in Greece recently, I'd posted a couple of progress reports to facebook about learning to swim. Having seen those status updates, my friend knew that I'd been taking lessons from boyfriend T.

"I don't find it easy," I reply, "but basically I can now swim for as long as I can hold my breath :-). Given that a few weeks ago I couldn't swim at all, I think that I'm making reasonable progress!"

"So you can't swim with your head above water at all?" asks my friend, surprised.

"No," I reply, "not yet anyway. I need to keep my head down in the water to make sure that I float!"

"Actually, while I was at the hotel in Mykonos," I continue, "I noticed that the other guests had various different swimming styles. I don't think that I'll ever be able to swim like some of them do."

"Why not?"

"Well, some of them are able to keep their entire head out of the water while they're swimming. I guess it's a type of breast stroke, but they never get their hair wet and they do it so slowly too, perhaps only one stroke a second. I admit that I don't sink now like I used to, but I only just float so I just couldn't keep my entire head dry!"

"I don't think people who swim like that are swimming properly," replies my friend, with a knowledgeable look on his face, "so don't worry. It doesn't matter if you're not able to do that."

"But don't you think that this relates to the basic physics?" I ask, pursuing the subject. "I mean, doesn't it means that people who can do that are much less dense than me? I'm sure that if I had been able to do that then I'd have learned to swim ages ago."

"Actually," I continue, "while I was on holiday, I bet boyfriend T that he couldn't swim like that, keeping his head out of the water the whole time."

"Why?" asks my friend, still chuckling to himself about the fact that I'd admitted to being 'dense'.

"Well he's quite a muscular guy, so I reckoned that means that he's also too dense to swim with his head out of the water the whole time."

"And were you right?"

"Actually it wasn't clear! The first day when he tried, he admitted to me that he couldn't do it. But a few days later he managed to do better, except that he was having to do about three strokes a second to keep his head dry, so I felt that that proved my point :-). Do you think a person's density affects their ability to swim?"

"I suppose it must have something to do with it," he replies, "but I reckon skill is much more important. It's probably 90% skill, and only 10% physics, something like that."

This morning, I did a bit of research using google and found (here) the following question with a couple of answers:
Question: Hi, I would just like to know the average density of a human being. Daphne, aged 16

Answer 1: Well, it's just about the same as that of water, because when you put the average human being in water, he just barely floats in it. Some people (me, for example) can sink or float depending on how much air they hold in their lungs, so their density can vary from just below to just above 1.0 g/cm^3. Grayce

Answer 2: Daphne, do you float in water? Some very muscular people don't. I hope that answers your question. Felix
So do very muscular people have trouble swimming? Or is my friend right after all, so that the physics only accounts for 10% of someone's swimming ability?

In some sense, posting this kind of question on my blog is a bit like 'Ask the audience' on Who wants to be a millionaire! It's not exactly reliable, but nonetheless it's always interesting to see other peoples views :-).

So if anyone has any thoughts on this, I'd be very interested to hear them!


John F said...

Fat floats!

As does air in the lungs.

As someone who through his genes has no fat on his limbs and a higher-than-average concentration on his torso, I can affirm that fat always floats in water. I'm constantly sinking feet-first when I pop in the water.

etre-moral-etre-sincere said...

basically I can now swim for as long as I can hold my breath <...> I need to keep my head down in the water to make sure that I float

That's exactly the stage I am in now. Since I recall that I started learning more or less the same time you did, it probably is normal for this stage!

By the way, can you float on your back? I am still having problems with that :-(

Nik_TheGreek said...

I grew up by the sea and swimming / floating comes like a second nature to me by now.
What I believe is that you should try to relax and enjoy the experience. You will be able to do anything, like floating on your back, in due time. Don't worry about it.
I think that heavier / muscular people might find it a bit more difficult to float but the difference is minimal. Everybody can stay floating on their back without moving any limp. It just needs some getting used to.

TSP said...

Hello GB,

My other half spent most of his young life in a pool while I spent some of mine in the sea. I was surprised to find that he could not enjoy the simple pleasure of floating on his back; his mid and legs just sink.

Another muscular friend who had a similar issue but wanted to compete in triathlons had a crack at following immersion swimming and seems to have been successful. It's one of many techniques which might work for you based on what you mention in your blog post.

Good luck !

Nine said...

I'm very muscly, but I float and swim like a fishy. Breathing control is important. In the pool, try going just out of your depth and experiment with breathing out (you'll sink) and holding your breath and relaxing.

Buoyancy is all about weight of water displaced, so yes, your density is important, as is the density of the water. Salt water is more dense so you float more easily. Same thing goes for chlorinated, hot/cold or aerated water (in which everybody sinks!!!)

I do think slot of it comes with confidence
and control.

benniboi said...

Sorry, I'm still giggling. It is funny that you actually tried to find some reason to justify why you can't swim with your head above water. Anyway, it is no point to learn how to swim with you hair dry and pretty, that's not the point for swimming in my opinion.
Basic posture of swimming: Breath in, head down, feet up, relax and float. Think about a plank of wood. OF course, if you want to be pretty and with dry hair after the work out, you can keep your head up. However, your legs and feet will naturally go down a bit, buoyancy will be changed. Then you have to paddle or move you feet to keep you going.

Shawn LI said...

agree with Benniboi, swimming is more about technique rather than your own "density" (it won't vary much among normal people anyway) As long as you can learn the right way to swim you will never sink

Take myself for example, after 8 years of swimming I still don't know freestyle (especially how to breath in freestyle) so I always increase my stroke frequency to keep myself afloat. But for breast stroke, I can do it very slowly (1 stroke every 10 sec) and still keep myself afloat

Was Once said...

Don't over think this. I see all kinds at the pool, from heavy and fat to thin and muscular...and all swim good enough. Get your head wet. I relearned to swim after serious brain injury(bi-lateral strokes) and my entire left is numb. I even at 40 learned to breathe on both sides while swimming freestyle(took in a lot of water and a year to get used to). The point is it can be done, you just have to decide to do it.

Tony said...

Hi GB,

It's techniques, so long you're comfortable with water, swimming with you head above the water is easy. =)

I think it's a useful skill to have, keeps the sunglasses dry! LOL

decisivemoment said...

Find some hot guy to "rescue" you, i.e. grab ahold of you with one arm around your chest, both of you facing up, him underneath you and using the other three limbs to do a sidestroke. That should relax you really fast, but also give you sort of an idea of what buoyancy feels like.

Basically your friend is right. Muscular people float more poorly than fat people but even fat people don't really float well enough to keep their head out of water, and the more you float the less you can propel yourself through the water. So it's swings and roundabouts really.

SuperchilledTrevor said...

I swim with some elite triathletes and they are lean, ie no fat and hence quite dense, but manage just fine. They do get cold faster though with less insulation... But in motion they're streamlined and have no breathing issues.

It is all about technique. Get a swimming coach to point you in the right direction and you'll avoid all the problems of poor technique. Swimming is so much fun and so relaxing, even at speed. It's kinda good to be able to breathe though.

Anonymous said...

aren't most competition swimmers muscley??? if they weren't they'd be not point in watching, would there??
I can float, swim head up or down or under the water but then again i am slim....
Some physcologists think that how we are with sex and sexuality can be seen on how confident we are in the water!!!! thoughts?

Anonymous said...


we want to see body shots of boyfriend T!

especially in his trunks! common! be a sport!

send high res pics =D

GB said...

Fascinating comments guys (and gals) :-). Indeed, much better than 'Ask the audience' on 'Who wants to be a millionaire'!

No etre-moral-etre-sincere, I'm no good at floating on my back either yet.

Thanks for the tip about immersion swimming TSP :-).

Well I do like to keep my blog entertaining, benniboi. And just to keep you giggling, I feel sure that I'm denser than average, because if anyone looks at my size they almost always underestimate my weight by 5-10 kg!

Very interesting Anonymous commenter who signs himself Sx, whoever you are. But I completely disagree that confidence in the water relates to confidence with sexuality. I reckon I'm a perfect counterexample to that idea!

LOL last anonymous commenter but no can do! Boyfriend T is for my eyes only :-).

GB xxx

Anonymous said...

GB...try swimming with flippers on your feet as it gives immediate buoyancy and confidence. Then you can gradually wean yourself off the flippers. I started swimming late in life and now have no problems swimming laps on y own. Try it, you'll notice the difference.

Anonymous said...


let us see shots of boyfriend T!

please.....!!! pretty please???

i'll send you mine if you let me see his???

be a sport!!! =D

pojaya said...

It's important to get the basics of swimming right.... after that you should be able whatever you want in the water!

I suspect it will take months, if not years, to become totally comfortable in the water.