and wondering why do I sit on the bottom of the bath but sitting on the bottom of a swimming pool is quite an effort?
Why do I not sink in the pool or float in the bath? How big does the body of water need to be before I stop sinking and start floating?
Guessing it may be to do with weight of fairly solid legs compared to an air-filled torso?

Have you got a fart bubble to pop out at your knees yet?

and wondering why do I sit on the bottom of the bath but sitting on the bottom of a swimming pool is quite an effort?

When was the last time you sat in a swimming pool 6 inches deep?

You’ll find it’s an equivalent effort to sitting in the bath.

Edit: Archimedes explained it all a while ago…

My nan always used to say that I must have hollow legs, so I reckon that discounts your theory

This thread is useless without pics

Why do I not sink in the pool or float in the bath?

If you work it out, let me know. My OH was once trying to help me improve my swimming, telling me to “just lie back and float” – but if I breathe out I can lie down on the bottom of a swimming pool.

You float if you displace a volume of water whose weight is equal to your weight.

Have you got a fart bubble to pop out at your knees yet?

Easy peasy 😆

If you work it out, let me know. My OH was once trying to help me improve my swimming, telling me to “just lie back and float” – but if I breathe out I can lie down on the bottom of a swimming pool.

Me too, except I don’t even have to breathe out, I just sink.

That RNLI “stay calm and float, then start swimming” advert is rubbish. I’d stay calm, sink to the bottom and then start walking to shore!

I’d probably float now I’ve got a bit more fat, but I once took great pleasure in demonstrating my ability to sink to the bottom of a swimming pool to an instructor who’d said that if you just lie in the right position you’ll float. I didn’t have to breath out either, not when I was at my racing weight – muscle and bone is denser than water and anybody with a lean athlete build will sink (like Michael Phelps just to pick a random example – I bet he sinks like a stone).

That RNLI “stay calm and float, then start swimming” advert is rubbish. I’d stay calm, sink to the bottom and then start walking to shore!

You should float,

Muscle has a density of 1.06 g/cm3
Fat has a density of 0.9 g/cm3
Bone around 2.9 to 3.8 g/cm3 depending on sex, diet, age and exercise.

But on top of that you have about 6l (about 7-10% of your total volume) of air in your lungs which will keep you afloat. So if you lie back you will float with your head above water. You’ll also have air trapped in your clothes so taking a moment to adjust keeps it there before you have to start planning what you’re going to do next.

If you hit the water, panic, breath out and thrash all the air out of your clothes then you’ll probably sink (or get cold water shock).

If you breath out completely most people will sink (you don’t need to be that skinny to do it, sorry to dssapoint) even tubby funsters can have their body fat measured by weighing themselves underwater.

“Having a bath”

How 1950’s dear boy.

even tubby funsters can have their body fat measured by weighing themselves underwater.

I’m not so sure. My sister is a walloper and is unsinkable. You’d have to push her down with a hydraulic ram for that body fat calculation.

I can float in a deep bath if I allow my feet to take the weight of my legs.

bikebouy – Member
“Having a bath”

How 1950’s dear boy.

You mean that your modern new-build house hasn’t got space for a bath?

I can float in a deep bath if I allow my feet to take the weight of my legs.

That’s what I was trying to do, doddle in the pool, much harder (impossible!) in 18″ of bathwater.

You float if you displace a volume of water whose weight is equal to your weight.

So why would I displace less water in a bath than I do in a pool? Yes, I know there is less water in there, but there is still more water than body if I have a nice deep one so I should still displace the same amount in absolute terms, just a greater proportion of the available water?

So if you lie back you will float with your head above water.

I definitely don’t float. I know the technique, because I used to do it as a kid – but now I am older and have cyclist legs they sink first.

I can float back-up though with my head in the water, like a dead body, but that’s not much use.

So why would I displace less water in a bath than I do in a pool?

Because half your body is sticking out of the water so not displacing any. But it still weighs. In a big enough bath you’d behave the same as in a swimming pool because that’s what a swiming pool is.

allow my feet to take the weight of my legs

I call that standing rather than sitting.

how cold does the water have to be for me to float when in the shower?

Me too, except I don’t even have to breathe out, I just sink.

Thank God it’s not just me that’s broken. Mrs Funk has given up trying to get me to float. I always sink.

What I can’t understand is how come the steel boat I’m currently in is floating and not sinking. Steel?!?!?!

Makes. No. Sense.

Maybe it’s actually got wheels and is rolling along on the bottom?

The boat is displacing water so it’s sinking. It’ll sink until the mass of air + steel + whatever else is the same as the mass of water displaced, then it’ll stop sinking and float. Add some more steel ( eg cargo) and it’ll sink a bit more. Add too much and down it’ll go
Knock a hole in the hull, being heavier water will displace the air and as water+steel is heavier than water, down it’ll go

Also for the OP – water is not at a constant density – deeper water is more dense due to the pressure of the water column above it. density affects the buoyancy of objects in a fluid – more dense fluid = more buoyant objects. So a bath has very little density but a 2 M deep pool is more dense at 2 M so you’re more likely to float away from the bottom, but maybe not rise all the way to the (less dense) surface. 2 M doesn’t sound like much but recreational scuba divers use their air supply to maintain neutral buoyancy and staying neutrally buoyant is pretty much a constant process, adding and dumping air as you go

Sounds good BBSB, makes sense. In a bath the water is confined on all sides and below, it can only rise when I get in, so even though it may be deeper than I am high (laying down) why don’t I sink only as far as the boat in your example when it’s displaced it’s own weight, why do I carry on down to the bottom, I must have displaced more than my own weight in water by then?
.
(My bath is quite wee but my parents have a huge 1950s enamel bath and I can pretty much lay down in that) Even as a very small child when the bath was loads bigger than me I would sink