# buoyancy **URL:** \ **Category:** Factual Questions\ **Created:** [October 6, 2000, 11:22pm UTC](https://boards.straightdope.com/t/buoyancy/36016 "2000-10-06T23:22:56Z")\ **Posts on this page:** 12\ **Page:** 1
**Author:** ![system\_hoser](https://avatars.discourse-cdn.com/v4/letter/s/a9adbd/32.png) [@system\_hoser](https://boards.straightdope.com/u/system_hoser)\ **Post date:** [October 6, 2000, 11:22pm UTC](https://boards.straightdope.com/t/buoyancy/36016/1 "2000-10-06T23:22:56Z")
Is there a liquid that a person can not swim in due to the inability to become buoyant in that liquid? Let’s say the swimmer is invulnerable to temperature, acid, blah blah blah and the only issue is whether or not the swimmer can become buoyant. Is there a liquid that could not support a swimming person? ---
**Author:** ![starfish](https://avatars.discourse-cdn.com/v4/letter/s/87869e/32.png) [@starfish](https://boards.straightdope.com/u/starfish)\ **Post date:** [October 6, 2000, 11:37pm UTC](https://boards.straightdope.com/t/buoyancy/36016/2 "2000-10-06T23:37:23Z")
A person is basically water. There are some heavier components but there is also air filled areas. If the liquid is significantly less dense than water he can’t swin for an extended time. He can always swim a short distance, the same as he can swim in air [jump]. You can also aerate water to make it less dense. ---
**Author:** ![kanicbird](https://avatars.discourse-cdn.com/v4/letter/k/5f8ce5/32.png) [@kanicbird](https://boards.straightdope.com/u/kanicbird)\ **Post date:** [October 6, 2000, 11:39pm UTC](https://boards.straightdope.com/t/buoyancy/36016/3 "2000-10-06T23:39:31Z")
my wag is a light grade petrolium or liquid natural gas. Probally liquid hydrogen would be the lightest (least dense) liquid. Even though a person would not be bouyant, doesn’t mean he will sink, the person could expend energy to stay afloat (swim) ---
**Author:** ![sailor](https://avatars.discourse-cdn.com/v4/letter/s/a587f6/32.png) [@sailor](https://boards.straightdope.com/u/sailor)\ **Post date:** [October 8, 2000, 3:15am UTC](https://boards.straightdope.com/t/buoyancy/36016/4 "2000-10-08T03:15:00Z")
I cannot think of any common liquid that would be lighter than water by a great margin. Ethanol is about 0.79… just try not to swallow too much. ---
**Author:** ![Tristan](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/tristan/32/18058_2.png) [@Tristan](https://boards.straightdope.com/u/Tristan)\ **Post date:** [October 8, 2000, 4:46am UTC](https://boards.straightdope.com/t/buoyancy/36016/5 "2000-10-08T04:46:59Z")
How about mercury? The difficult part might be breaking the surface tension… I’m not sure how that works, but I do know that you can float lead ingots on mercury… talk about weird things to see… But I don’t know how density would affect surface tension…I don’t know if you would sink in an inch or so, or if it would work like a water bed, and keep you on the surface, although maybe in a depression… hmmmm… Any thoughts from the scientist community out there?? ---
**Author:** ![RM\_Mentock](https://avatars.discourse-cdn.com/v4/letter/r/e274bd/32.png) [@RM\_Mentock](https://boards.straightdope.com/u/RM_Mentock)\ **Post date:** [October 8, 2000, 1:30pm UTC](https://boards.straightdope.com/t/buoyancy/36016/6 "2000-10-08T13:30:37Z")
> [@](#): > > \*Originally posted by sailor \* > **I cannot think of any common liquid that would be lighter than water by a great margin. Ethanol is about 0.79** I think you have your answer, system\_hoser. Especially if this is research for a murder mystery that you are writing. ---
**Author:** ![cry2cin](https://avatars.discourse-cdn.com/v4/letter/c/c5a1d2/32.png) [@cry2cin](https://boards.straightdope.com/u/cry2cin)\ **Post date:** [October 8, 2000, 8:07pm UTC](https://boards.straightdope.com/t/buoyancy/36016/7 "2000-10-08T20:07:20Z")
Mercury might apply. ---
**Author:** ![RM\_Mentock](https://avatars.discourse-cdn.com/v4/letter/r/e274bd/32.png) [@RM\_Mentock](https://boards.straightdope.com/u/RM_Mentock)\ **Post date:** [October 8, 2000, 8:29pm UTC](https://boards.straightdope.com/t/buoyancy/36016/8 "2000-10-08T20:29:41Z")
> [@](#): > > \*Originally posted by cry2cin \* > \*\*Mercury might apply. \*\* Except that, surely, you would not be inable to become buoyant in mercury? ---
**Author:** ![cry2cin](https://avatars.discourse-cdn.com/v4/letter/c/c5a1d2/32.png) [@cry2cin](https://boards.straightdope.com/u/cry2cin)\ **Post date:** [October 8, 2000, 9:15pm UTC](https://boards.straightdope.com/t/buoyancy/36016/9 "2000-10-08T21:15:42Z")
Of course! Warum nicht? ---
**Author:** ![Tristan](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/tristan/32/18058_2.png) [@Tristan](https://boards.straightdope.com/u/Tristan)\ **Post date:** [October 8, 2000, 11:29pm UTC](https://boards.straightdope.com/t/buoyancy/36016/10 "2000-10-08T23:29:42Z")
> [@](#): > > \*Originally posted by cry2cin \* > \*\*Of course! Warum nicht? \*\* I posted on this above… what do you guys think…? heheh ---
**Author:** ![TNTruth](https://avatars.discourse-cdn.com/v4/letter/t/d9b06d/32.png) [@TNTruth](https://boards.straightdope.com/u/TNTruth)\ **Post date:** [October 9, 2000, 11:24am UTC](https://boards.straightdope.com/t/buoyancy/36016/11 "2000-10-09T11:24:36Z")
Any grade of oil, from residual bunker fuel to gasoline, is less dense than water. If you fall into a tank full of it you will sink like a stone. ---
**Author:** ![system\_hoser](https://avatars.discourse-cdn.com/v4/letter/s/a9adbd/32.png) [@system\_hoser](https://boards.straightdope.com/u/system_hoser)\ **Post date:** [October 9, 2000, 5:36pm UTC](https://boards.straightdope.com/t/buoyancy/36016/12 "2000-10-09T17:36:18Z")
Thanks to everyone for the replies. I think TnTruth’s reply is the one that scares me the most; knowing that even though I can swim there is still something fairly common that I could fall into and sink like a stone.