# How exactly does a boat float? **URL:** \ **Category:** Factual Questions\ **Created:** [June 21, 2003, 12:30am UTC](https://boards.straightdope.com/t/how-exactly-does-a-boat-float/183317 "2003-06-21T00:30:22Z")\ **Posts on this page:** 10\ **Page:** 5
**Author:** ![DanBlather](https://avatars.discourse-cdn.com/v4/letter/d/f4b2a3/32.png) [@DanBlather](https://boards.straightdope.com/u/DanBlather)\ **Post date:** [June 24, 2003, 4:44pm UTC](https://boards.straightdope.com/t/how-exactly-does-a-boat-float/183317/81 "2003-06-24T16:44:06Z")
> [@](#): > > \*Originally posted by Nanu \* > \*\*Another example is in the design of dams… > The force that the dam must hold back is only a function of how tall the dam is. > a dam 200ft tall and with a reservoir 100 miles long has to be just as strong as a dam 200ft tall but with a reservoir that goes back only a few inches. > the force that water exerts on an object (what keeps a sip afloat) depends only on the pressure of said water, in other words, the height of the column of water, not the volume of it. \*\* Holy Crap! That nicely illustrates why it is so important to have drain holes in a retaining wall. ---
**Author:** ![PeeWee](https://avatars.discourse-cdn.com/v4/letter/p/c0e974/32.png) [@PeeWee](https://boards.straightdope.com/u/PeeWee)\ **Post date:** [June 24, 2003, 4:47pm UTC](https://boards.straightdope.com/t/how-exactly-does-a-boat-float/183317/82 "2003-06-24T16:47:36Z")
Tastycorn, I’ll give 'em a shot. Hydrofoils are not really my expertise though. Also, don’t expect immediate replies, it amazes me how much time some of the regular posters must spend on this board! ---
**Author:** ![sailor](https://avatars.discourse-cdn.com/v4/letter/s/a587f6/32.png) [@sailor](https://boards.straightdope.com/u/sailor)\ **Post date:** [June 24, 2003, 6:04pm UTC](https://boards.straightdope.com/t/how-exactly-does-a-boat-float/183317/83 "2003-06-24T18:04:39Z")
This thread is beginning to remind me of the one where it was asked [what made ships stand upright and not tip over](http://boards.straightdope.com/sdmb/showthread.php?s=&threadid=149840) and we kept going around in circles until I threw up my hands in despair and gave up. ---
**Author:** ![Student\_Tim](https://avatars.discourse-cdn.com/v4/letter/s/a698b9/32.png) [@Student\_Tim](https://boards.straightdope.com/u/Student_Tim)\ **Post date:** [July 8, 2010, 12:45pm UTC](https://boards.straightdope.com/t/how-exactly-does-a-boat-float/183317/84 "2010-07-08T12:45:29Z")
For all off you who, like me, are looking for an answer to the question stated above: IGNORE Omar’s comments, he will get you confused, and ONLY read Robby. I read the first 60 comments, but all you need are his. My professor asked me how it was possible, and now I know the answer. Thanks. ---
**Author:** ![DrFidelius](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/drfidelius/32/3447_2.png) [@DrFidelius](https://boards.straightdope.com/u/DrFidelius)\ **Post date:** [July 8, 2010, 12:48pm UTC](https://boards.straightdope.com/t/how-exactly-does-a-boat-float/183317/85 "2010-07-08T12:48:59Z")
Whiskey Tango Foxtrot! Is this Zombie Thread Thursday? ---
**Author:** ![Machine\_Elf](https://avatars.discourse-cdn.com/v4/letter/m/82dd89/32.png) [@Machine\_Elf](https://boards.straightdope.com/u/Machine_Elf)\ **Post date:** [July 8, 2010, 1:07pm UTC](https://boards.straightdope.com/t/how-exactly-does-a-boat-float/183317/86 "2010-07-08T13:07:34Z")
> [@Omar](#): > > Ok, robby. Answer me this. > > If you take a ship from a mold, to a narrow canal, to an ocean, does the MINIMUM amount of water needed to keep that ship afloat in each body of water change? Robby’s exact quote: > [@Robby](#): > > The point is that is does not matter what volume of water surrounds the ship, so long as the ship is completely immersed below the waterline. The ship can be in a matched mold, a narrow canal, or the ocean. There’s an important condition in there that you (Omar) seem to have overlooked: **“…so long as the ship is completely immersed below the waterline.”** It doesn’t matter what shape/size the container is, or how much water is used, **so long as the ship is completely immersed below the waterline.** ---
**Author:** ![robby](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/robby/32/11048_2.png) [@robby](https://boards.straightdope.com/u/robby)\ **Post date:** [July 8, 2010, 4:31pm UTC](https://boards.straightdope.com/t/how-exactly-does-a-boat-float/183317/87 "2010-07-08T16:31:54Z")
> [@Student\_Tim](#): > > For all off you who, like me, are looking for an answer to the question stated above: > > IGNORE Omar’s comments, he will get you confused, and ONLY read Robby. I read the first 60 comments, but all you need are his. Well, thanks for the compliment! 🙂 The funny thing is that I didn’t even remember this thread when I first started reading it a few moments ago. I was actually starting to formulate a response when I ran into all of my old posts. Has it really been 7 years? :eek: ---
**Author:** ![beowulff](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/beowulff/32/542_2.png) [@beowulff](https://boards.straightdope.com/u/beowulff)\ **Post date:** [July 8, 2010, 5:06pm UTC](https://boards.straightdope.com/t/how-exactly-does-a-boat-float/183317/88 "2010-07-08T17:06:21Z")
> [@DrFidelius](#): > > Whiskey Tango Foxtrot! > > Is this Zombie Thread Thursday? We need to know how much water it takes to float a Zombie! ---
**Author:** ![DrFidelius](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/drfidelius/32/3447_2.png) [@DrFidelius](https://boards.straightdope.com/u/DrFidelius)\ **Post date:** [July 8, 2010, 5:48pm UTC](https://boards.straightdope.com/t/how-exactly-does-a-boat-float/183317/89 "2010-07-08T17:48:34Z")
How to make a Zombie float? Two scoops of ice cream, some soda, one Zombie… ---
**Author:** ![UncleRojelio](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/unclerojelio/32/3160_2.png) [@UncleRojelio](https://boards.straightdope.com/u/UncleRojelio)\ **Post date:** [July 8, 2010, 6:14pm UTC](https://boards.straightdope.com/t/how-exactly-does-a-boat-float/183317/90 "2010-07-08T18:14:52Z")
Between this thread and the linked thread about CG vs CB … wait, where the did the day go? Don’t let anyone tell you that zombies aren’t dangerous. [Previous page](https://boards.straightdope.com/t/how-exactly-does-a-boat-float/183317.md?page=4)