# Without sponges

**URL:** <https://boards.straightdope.com/t/without-sponges/350769>\
**Category:** Cecil's Columns/Staff Reports\
**Created:** [March 31, 2006, 10:12pm UTC](https://boards.straightdope.com/t/without-sponges/350769 "2006-03-31T22:12:46Z")\
**Posts on this page:** 5\
**Page:** 1

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**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:** [March 31, 2006, 10:12pm UTC](https://boards.straightdope.com/t/without-sponges/350769/1 "2006-03-31T22:12:46Z")

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In [this week’s column](http://www.straightdope.com/columns/060331.html), Cecil is asked (and is still thinking about) “How much deeper would the ocean be without sponges?” That’s an old joke. Besides, take something out of the ocean and it’s going to be less deep, not more.

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**Author:** ![PetW](https://avatars.discourse-cdn.com/v4/letter/p/d2c977/32.png) [@PetW](https://boards.straightdope.com/u/PetW)\
**Post date:** [April 1, 2006, 5:50pm UTC](https://boards.straightdope.com/t/without-sponges/350769/2 "2006-04-01T17:50:29Z")

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> [@RM Mentock](#):
>
> In [this week’s column](http://www.straightdope.com/columns/060331.html), Cecil is asked (and is still thinking about) “How much deeper would the ocean be without sponges?” That’s an old joke. Besides, take something out of the ocean and it’s going to be less deep, not more.

Cite?

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**Author:** ![Johnny\_L.A](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/johnny_l.a/32/1084_2.png) [@Johnny\_L.A](https://boards.straightdope.com/u/Johnny_L.A)\
**Post date:** [April 1, 2006, 6:19pm UTC](https://boards.straightdope.com/t/without-sponges/350769/3 "2006-04-01T18:19:29Z")

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> [@PetW](#):
>
> Cite?

The joke is that if the sponges were not in the ocean, then the water they hold would add to the volume. (You knew that, of course.) But sponges are not 100% water. Consider this analogy: You have an aquarium with a brick in it. If you remove the brick, the volume of water doesn’t change but the level of the water goes down. So if you remove the sponge itself, which has a solid structure, then the water level will decrease. Of course water is constantly being added by rain and rivers, and is being lost through evaporation. And compared to the volume of the oceans the volume of the sponges is insignificant. But in a ‘perfect system’ (e.g., an aquarium that is packed with sponges and water, and assuming that you can remove 100% of the water from the sponges and return it to the tank without any evaporation, etc.) then the water level will go down.

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**Author:** ![PetW](https://avatars.discourse-cdn.com/v4/letter/p/d2c977/32.png) [@PetW](https://boards.straightdope.com/u/PetW)\
**Post date:** [April 16, 2006, 11:21pm UTC](https://boards.straightdope.com/t/without-sponges/350769/4 "2006-04-16T23:21:37Z")

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> [@RM Mentock](#):
>
> Besides, take something out of the ocean and it’s going to be less deep, not more.

What if you take out dirt from the bottom of the ocean?

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**Author:** ![naita](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/naita/32/5862_2.png) [@naita](https://boards.straightdope.com/u/naita)\
**Post date:** [April 17, 2006, 10:15am UTC](https://boards.straightdope.com/t/without-sponges/350769/5 "2006-04-17T10:15:28Z")

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> [@PetW](#):
>
> What if you take out dirt from the bottom of the ocean?

It will be slightly deeper where most of the dirt is, i.e. some of the shallower areas. And slightly shallower where there was little dirt.